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TTL

TTL is a three-letter acronym with multiple meanings. This article provides an overview and links to articles on the major uses of the term. == Through-the-lens metering (Photography) == A light metering system in cameras that measures light passing through the lens. == Transistor–transistor logic (Electronics) == A class of digital logic circuits using bipolar junction transistors for logic gates and integrated circuits. == Time to live (Computing and networking) == A mechanism in packet-switched networks to prevent routing loops by limiting packet lifespan. == Other uses ==

Through-the-lens metering (Photography)

Principles and operation

Through-the-lens (TTL) metering is a photographic exposure measurement system in which the camera evaluates the intensity of light reflected from the subject as it passes through the camera's taking lens, enabling precise determination of aperture, shutter speed, and ISO settings for optimal exposure.^[1] In typical single-lens reflex (SLR) cameras, light enters the lens and encounters a partially silvered main mirror or beamsplitter, which directs a portion of the incoming rays to a dedicated photocell or photosensor positioned within the viewfinder assembly or a separate metering chamber in the camera body.^[2] This setup ensures the meter "sees" the same field of view and optical characteristics as the film or image sensor, providing readings that reflect the actual scene composition viewed by the photographer.^[3] TTL systems operate in two primary configurations based on aperture control: full-aperture metering and stop-down metering. In full-aperture metering, measurements are taken with the lens diaphragm wide open to maximize light transmission to the sensor for brighter, more sensitive readings; the camera body receives aperture value information via mechanical coupling (such as pins or levers on the lens mount) to compensate computationally for the reduction in light when the diaphragm stops down to the selected f-stop just before exposure.^[2] This approach yields a consistently bright viewfinder image and seamless operation but requires compatible lenses with signaling mechanisms.^[4] Conversely, stop-down metering involves manually or automatically closing the diaphragm to the working aperture prior to measurement, directly assessing the light at the intended exposure level without needing electronic or mechanical aperture communication; while simpler for non-coupled lenses, it results in a darker viewfinder and potential metering inaccuracies in low light due to reduced illumination on the sensor.^[4] Advanced TTL implementations include off-the-film (OTF) metering, which measures light during the actual exposure rather than beforehand. In OTF systems, the sensor—a small silicon photodiode typically located near the film plane or behind the shutter—captures light reflected directly from the film's emulsion surface after the mirror flips up and the shutter opens, allowing real-time adjustment of flash duration or exposure until the desired light integral is reached.^[5] This contrasts with conventional pre-exposure TTL, where metering occurs via mirror reflection without direct film involvement, potentially missing variations in film reflectivity.^[6] OTF sensor placement ensures precise compensation for the film's response, though it can vary readings by up to half a stop depending on emulsion type.^[6] A key advantage of TTL metering over external handheld meters is its automatic accounting for lens-specific factors that alter light transmission, such as neutral density filters, teleconverters, bellows extensions, or macro tubes, which would otherwise require manual exposure adjustments.^[3] By integrating the measurement directly into the optical path, TTL eliminates errors from misalignment between the meter and lens viewpoint, enhancing accuracy in complex setups.^[7] TTL facilitates sophisticated metering patterns that analyze the scene as composed through the lens, improving exposure reliability across diverse lighting conditions. Evaluative or matrix metering divides the frame into multiple zones (e.g., 63 in some systems) and weighs inputs algorithmically, prioritizing the focus point while considering overall tonal balance for even exposures in varied scenes like landscapes.^[1] Center-weighted metering emphasizes the central 60-80% of the frame, de-emphasizing edges to preserve detail in portraits or subjects against bright backgrounds.^[7] Spot metering targets a narrow 1-5% area at the selected focus point, ideal for high-contrast situations where precise tonal control is needed, such as isolating a shadowed subject.^[1] These patterns leverage TTL's view-matched readings to deliver context-aware results unattainable with external meters.^[3]

History and evolution

The development of through-the-lens (TTL) metering in photography began in the early 1960s, marking a significant advancement in single-lens reflex (SLR) camera technology by allowing photographers to measure light directly through the camera lens for more accurate exposure control. The first 35mm SLR with TTL metering was the Topcon RE Super, introduced in 1963, which used cadmium sulfide (CdS) photocells positioned behind a partially silvered reflex mirror to provide average light readings across the frame.^[8] This innovation eliminated the need for separate handheld exposure meters and set the stage for integrated systems in subsequent models. In 1966, the Olympus Pen FT half-frame SLR incorporated a partial TTL CdS meter that provided exposure value (EV) readings matched to lens markings, offering an early example of TTL in a compact format, though it required manual adjustments.^[9] A pivotal milestone came in 1966 with the Minolta SRT 101, which introduced full-aperture TTL metering with a match-needle display in the viewfinder, enabling brighter viewing and more precise readings without stopping down the lens.^[10] This system, using off-the-lens cells coupled to the lens aperture, became highly influential for its reliability and ease of use in professional workflows. Building on this, the Canon F-1, launched in 1971, integrated TTL full-aperture metering with the new FD lens mount, providing center-weighted readings via a viewfinder needle display and supporting interchangeable focusing screens for varied metering patterns.^[11] Similarly, the Nikon F2 Photomic S, released in 1973, refined TTL metering with an LED-based finder for improved low-light sensitivity and center-weighted patterns, solidifying Nikon's dominance in professional SLRs.^[12] By the 1980s, TTL metering evolved further through integration with autofocus systems in SLRs, enhancing speed and automation for dynamic shooting scenarios. The Minolta Maxxum 7000, introduced in 1985, was the first production autofocus 35mm SLR with TTL metering, combining phase-detection AF with evaluative light measurement to enable rapid subject tracking and exposure adjustments. This period also saw advancements in flash metering, with Olympus pioneering off-the-film (OTF) TTL in the 1975 OM-2, which measured light directly on the film plane during exposure to overcome inconsistencies in pre-flash or ambient predictions, though full OTF flash integration expanded in the 1980s across brands.^[13] The transition to digital photography in the late 1990s and 2000s adapted TTL metering for electronic sensors, maintaining core principles while incorporating computational enhancements. Canon's EOS series, starting with the 1995 film-based Elan II (EOS 50), introduced E-TTL flash metering using pre-flash evaluation for distance-aware exposure, which carried over to digital models like the 2000 EOS D30 and later DSLRs.^[14] Nikon followed with D-TTL in the 1999 D1 and evolved to i-TTL in 2003 with the D2H, employing matrix metering and pre-flash for precise fill-flash in digital SLRs.^[15] In mirrorless systems, Sony's Alpha series from 2006 utilized ADI (Advanced Distance Integration) TTL, leveraging lens data and pre-flash for seamless metering in compact bodies like the A100.^[5] Early TTL implementations faced challenges, particularly with stop-down metering in 1960s models like the Canon FT QL, where closing the aperture to measure light caused temporary viewfinder blackout, complicating composition.^[16] This was largely resolved by mid-decade full-aperture systems in cameras like the Minolta SRT 101, which maintained a bright viewfinder, and further refined by OTF metering in the Olympus OM-2, which eliminated pre-exposure errors by reading light during the actual shot.^[17] The evolution of TTL metering profoundly impacted photography by shifting from labor-intensive manual exposure to automated precision, enabling high-speed action capture, consistent fill-flash in mixed lighting, and creative experimentation without metering interruptions.^[18] These advancements democratized professional techniques, boosting productivity in photojournalism and event photography while laying the foundation for modern evaluative metering in digital cameras.^[19]

Transistor–transistor logic (Electronics)

Fundamentals and components

Transistor-transistor logic (TTL) is a family of digital logic circuits implemented using bipolar junction transistors (BJTs), primarily NPN types, where the transistors function both as switches and amplifiers to process binary signals.^[20] Developed in the 1960s, TTL circuits integrate multiple transistors, diodes, and resistors on a single monolithic chip to perform logic operations, with the standard 7400 series operating at a 5 V supply voltage.^[21] At its foundation, TTL relies on binary logic principles, where basic operations such as AND (output high only if all inputs high), OR (output high if any input high), and NOT (inverts the input) form the building blocks for more complex gates, though TTL implementations emphasize efficient switching over discrete realizations.^[22] The core components of a TTL circuit include a multi-emitter input transistor that inherently provides AND logic functionality, a phase-splitter transistor to drive the output stage, and a totem-pole output configuration consisting of upper and lower transistors in a push-pull arrangement for bidirectional current drive.^[20] The multi-emitter transistor, typically Q1, has multiple emitter terminals connected to the inputs, allowing a single base-collector junction to handle multiple signals; if any input is low, it forward-biases the base-emitter junction, saturating the transistor and pulling its collector low.^[22] The phase splitter (Q2) is an NPN transistor whose base is driven by Q1's collector; its collector connects to the base of the upper output transistor, while its emitter drives the lower one, ensuring complementary switching.^[20] The totem-pole output stage features a Darlington pair for the active pull-up transistor (providing high current gain to minimize loading on the phase splitter) paired with a passive pull-down resistor or active NPN for low output, enabling the circuit to source and sink current efficiently.^[23] Standard TTL defines logic levels to ensure reliable noise margins and interoperability: a high input voltage (V_IH) must be at least 2 V, while a low input voltage (V_IL) must not exceed 0.8 V; correspondingly, output high (V_OH) is at least 2.4 V, and output low (V_OL) is at most 0.4 V, all referenced to a 5 V supply.^[24] These levels allow TTL gates to interface seamlessly, with outputs swinging near the rails but conservatively specified to account for loading effects.^[21] A basic TTL NAND gate exemplifies these elements, serving as the foundational building block for the family. The circuit typically comprises five NPN transistors (Q1 to Q5), a diode, and several resistors. Inputs A and B connect to the emitters of Q1, a multi-emitter NPN whose base ties to a resistor from V_CC (5 V) and whose collector connects to the base of Q2 via a resistor; when both inputs are high (>2 V), Q1's base-emitter junctions are reverse-biased, keeping Q1 off and allowing Q2's base to go high.^[20] Q2, the phase splitter, then turns on, with its collector low (driving the Darlington pair Q4-Q5 off via a resistor and diode for speed-up) and its emitter high, saturating Q3 to pull the output low (implementing the NAND inversion).^[22] Conversely, if any input is low, Q1 saturates, pulling Q2's base low to turn Q2 off; Q2's collector then goes high, activating the Darlington pair (Q4 base-driven, Q5 emitter to output) to pull the output high near 3.4 V (limited by the Darlington V_BE drops), while a diode prevents Q3 from conducting.^[23] This configuration achieves the NAND function—Y = ¬(A ∧ B)—with the Darlington pair ensuring sufficient β gain (often >1000) for low drive current from Q2, typically around 1 mA, while supporting fan-outs up to 10 standard loads.^[20]

Electrical characteristics

Standard TTL circuits operate with a nominal supply voltage of 5 V, tolerant to variations between 4.75 V and 5.25 V, ensuring reliable performance within this range. Key performance parameters include a typical propagation delay of 10 ns per gate, power dissipation of approximately 10 mW per gate, and a fan-out capability of 10 standard loads, allowing each output to drive up to 10 similar inputs without degradation. Current requirements specify that outputs can sink up to 16 mA in the low state and source up to 400 μA in the high state, balancing drive capability with power efficiency. Noise margins in standard TTL are symmetric and relatively modest at 0.4 V for both high and low levels, defined by the voltage levels: minimum high-level output voltage (V_OH) of 2.4 V, maximum low-level output voltage (V_OL) of 0.4 V, minimum high-level input voltage (V_IH) of 2.0 V, and maximum low-level input voltage (V_IL) of 0.8 V. These margins are calculated using the equations:

\text{NM}_H = V_{OH} - V_{IH}

\text{NM}_L = V_{IL} - V_{OL}

yielding NM_H = 0.4 V and NM_L = 0.4 V, which provide basic immunity to noise but limit robustness in noisy environments. The speed-power product for standard TTL is approximately 100 pJ per gate, representing the trade-off between propagation delay (10 ns) and power dissipation (10 mW), calculated as the product of these values; this relatively high figure contributes to thermal challenges in large-scale integrated circuits, often necessitating cooling for dense designs.^[20] Environmental factors influence TTL performance, with the recommended operating free-air temperature range of 0°C to 70°C for commercial-grade devices; propagation delay typically increases over this full range due to temperature-induced variations in transistor characteristics, requiring derating considerations for high-reliability applications. Additionally, the low noise margins render TTL susceptible to input voltage spikes exceeding 400 mV, which can approach or surpass the input thresholds and cause erroneous switching, particularly in environments with electromagnetic interference.^[25]

Applications and variants

Transistor-transistor logic (TTL) found widespread application in early digital electronics, particularly through the 7400 series of integrated circuits developed by Texas Instruments. The 7400 quad 2-input NAND gate, introduced in 1966, served as a foundational building block for logic operations in systems requiring reliable bipolar switching.^[26] These ICs were extensively used in digital calculators for arithmetic and control functions, as well as in early microcomputers like the Altair 8800, where TTL components handled address decoding, memory interfacing, and peripheral control on the S-100 bus.^[27] Over time, TTL evolved into several variants to address trade-offs in speed, power, and compatibility. The Low-Power Schottky (LS-TTL) family, such as the 74LS series, incorporated Schottky diodes to prevent transistor saturation, achieving a typical propagation delay of around 10 ns while reducing power dissipation to about 2 mW per gate—offering a balanced performance for many applications.^[28] Advanced Schottky (AS-TTL) variants further optimized speed, with propagation delays as low as 1.5–3 ns, at the cost of higher power consumption up to 20 mW per gate, making them suitable for high-performance logic.^[29] For interfacing with emerging CMOS technologies, High-speed CMOS TTL-compatible (HCT) devices were developed, featuring TTL-level inputs (thresholds of 2 V high and 0.8 V low) while retaining CMOS's low static power draw of less than 1 µW per gate.^[30] Compared to alternatives, TTL provided superior speed in the 1970s, with standard variants offering 10–15 ns delays versus CMOS's initial 25–50 ns, though CMOS excelled in power efficiency (milliwatts versus microwatts at rest).^[31] Emitter-coupled logic (ECL) achieved even faster 1 ns delays but consumed far more power (50–100 mW per gate), limiting it to specialized high-speed uses.^[32] TTL's role diminished with the VLSI transition in the 1980s, as CMOS scaling enabled denser, lower-power integration, but TTL influenced early programmable logic devices (PLDs) like programmable array logic (PAL) chips, which used TTL-compatible bipolar processes as precursors to modern field-programmable gate arrays (FPGAs).^[29] Today, TTL persists in legacy and niche roles, including hobbyist prototyping for its robust 5 V operation and availability, as well as automotive electronics where radiation-hardened variants ensure reliability in harsh environments.^[33] However, new designs overwhelmingly favor CMOS for its scalability and energy efficiency, with TTL largely supplanted post-1980s except in maintenance of older systems.^[34] The 74LS series remains a go-to for balanced speed-power needs in such contexts, exemplifying TTL's enduring practicality.^[35]

Time to live (Computing and networking)

Definition and purpose

Time to live (TTL) is a mechanism in computing and networking that limits the lifespan of data packets or records by using a counter embedded in their headers or metadata, which decrements with each hop or processing step until it reaches zero, at which point the data is discarded to prevent indefinite circulation.^[36] In the context of Internet Protocol (IP) networking, TTL serves as an 8-bit field in the IPv4 header, representing the maximum time in seconds a datagram can exist in the network, though it is commonly interpreted and decremented as a hop count by routers.^[36] The primary purpose of TTL is to enhance network efficiency by ensuring stale or undeliverable data expires, thereby conserving resources and avoiding congestion from endless loops, such as in routing failures or broadcast storms where packets could otherwise propagate infinitely in multicast or broadcast scenarios.^[36] It also bounds the lifetime of packets to protect higher-level protocols from disruption by old duplicates, promoting reliability in dynamic environments.^[36] By discarding packets that exceed their TTL, the mechanism prevents resource exhaustion and maintains overall system stability.^[37] TTL originated in the mid-1970s as part of the DARPA Internet Protocol design to support flexible routing across interconnected networks like ARPANET, addressing the need to tolerate transient inconsistencies without network-level failure notifications.^[37] It was formally standardized in IPv4 through RFC 791 in 1981, defining an 8-bit field with a maximum value of 255 hops or seconds.^[36] In general operation, the sender initializes the TTL value—often 64 or 128 for typical internet paths—and each router or processing point decrements it by at least 1; if it reaches zero before delivery, the packet is dropped, and an ICMP Time Exceeded message may be sent back to the source for diagnostics.^[36] Beyond core networking, TTL concepts extend to other computing areas, such as DNS caching where it specifies how long resolvers store records before refreshing to ensure data freshness, or message queues like Azure Service Bus where per-message TTLs set expiration times to remove unprocessed items and prevent backlog accumulation.^[38]^[39]

Implementation in protocols

In the Internet Protocol version 4 (IPv4), the Time to Live (TTL) is an 8-bit field in the IP header that specifies the maximum number of hops a packet can traverse before being discarded, preventing indefinite looping in the network.^[40] Routers decrement the TTL by at least 1 upon forwarding; if it reaches zero, the packet is dropped, and an ICMP Time Exceeded message (Type 11, Code 0) is typically sent to the source. In IPv6, this field is renamed the Hop Limit, retaining the 8-bit size and similar functionality to explicitly count hops rather than imply time-based expiration.^[41] The traceroute utility exploits this mechanism by sending packets with incrementally increasing TTL values (starting from 1), eliciting ICMP Time Exceeded responses from each intermediate router to map the path to a destination.^[42] User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP) inherit the IP header's TTL field, applying it to error reporting and diagnostics. For instance, in ICMP echo requests used by the ping utility, the TTL (typically set to 64 or 128) limits the probe's overall reach; if it expires en route to the destination, an ICMP Time Exceeded message reports the failure, indicating the packet did not complete the round trip. The ping utility measures end-to-end round-trip time to the destination. In contrast, tools like traceroute vary the initial TTL (e.g., sending probes with TTL=1, 2, up to 30 or more) to elicit ICMP Time Exceeded responses from each hop, enabling network troubleshooting such as identifying the path and per-segment latencies, though firewalls may suppress ICMP responses, complicating diagnostics.^[43] In the Domain Name System (DNS), TTL refers to a 32-bit unsigned integer field in resource records (RRs) that dictates the caching duration for query responses in seconds, influencing how long resolvers store data before re-querying authoritative servers. Authoritative name servers set TTL values to balance server load reduction (via longer caching at recursive resolvers) against data freshness; low values (e.g., 300 seconds) ensure quick propagation of changes like IP address updates, while higher values (e.g., 86,400 seconds or one day) minimize query traffic for stable records.^[44] Misconfigured low TTLs can overload authoritative servers during high-traffic events, such as DNS changes for popular domains. Beyond core IP and DNS, TTL-like mechanisms appear in routing and multicast protocols to control propagation and scope. In Border Gateway Protocol (BGP), the Generalized TTL Security Mechanism (GTSM) mandates setting TTL to 255 for externally peered sessions, rejecting incoming packets with TTL below 255 to thwart spoofed control-plane attacks from remote sources, assuming direct adjacency between peers.^[45] Open Shortest Path First (OSPF) employs an LS Age field in link-state advertisements (LSAs)—a 16-bit value starting at 0 and incrementing in seconds—that functions analogously to TTL for aging out stale topology information; LSAs reach MaxAge (3600 seconds) and are flushed via reflooding, with proactive refreshes every 30 minutes to maintain database synchronization.^[46] For multicast, Internet Group Management Protocol (IGMP) messages carry TTL=1 to limit scope to the local network, while IP multicast datagrams use TTL thresholds (e.g., TTL=15 for organization-local) at routers to enforce administrative scoping, preventing unintended global propagation as defined in host extensions for multicasting.^[47] Best practices for TTL configuration emphasize defaults suited to network scale: many operating systems set initial TTL to 64 for local or enterprise environments (sufficient for up to 64 hops) or 128 for broader internet reach, with a maximum of 255 to avoid overflow while ensuring global traversability.^[48] Security considerations include mitigating TTL expiry attacks—where floods of low-TTL packets trigger excessive ICMP Time Exceeded responses, causing denial-of-service—through firewall rules that rate-limit or drop such ICMP messages and discard ingress packets with suspiciously low TTL (e.g., below 10).

Other uses

Automotive and business contexts

In the automotive industry, particularly in the United States, TTL refers to the combined fees for tax, title, and license that are added to the base price of a vehicle during purchase. These fees encompass state and local sales taxes on the vehicle's value (after any trade-in deduction), title transfer costs to register ownership with the state Department of Motor Vehicles (DMV), and license or registration fees to operate the vehicle legally. TTL applies to both new and used vehicles and is collected at the point of sale or shortly thereafter, often financed into the loan if applicable.^[49]^[50] The exact amount of TTL varies significantly by state, vehicle price, and local regulations, but combined state and local sales taxes typically range from 0% to over 10%, with a national average of about 7.5% (as of 2025).^[51] For instance, on a $30,000 vehicle, a 6-10% sales tax would add $1,800 to $3,000, while title and license fees often range from $100 to $500, depending on the state—such as $75.75 to $95.75 for title transfers in Florida. In states like New Hampshire, there is no sales tax on vehicle purchases, reducing TTL primarily to title and registration costs of around $25 to $100. The total vehicle cost is thus calculated as the base price plus TTL, influencing the out-the-door price quoted by dealerships and affecting consumer financing decisions.^[52]^[53] These TTL requirements trace their origins to early 20th-century vehicle registration laws, with all U.S. states mandating license plates by 1918 and most adopting formalized title systems in the 1920s to standardize ownership tracking and generate revenue for road infrastructure. This post-1920s framework impacted dealership pricing and consumer budgeting, as TTL became a fixed component of transactions amid rising auto registrations.^[54]^[55] In business and accounting contexts, TTL is sometimes used as an abbreviation for "total," particularly in invoices, ledgers, or financial summaries to denote the sum of line items before a grand total. This usage appears in expense tracking or billing statements to simplify aggregation of costs. Unlike total cost of ownership (TCO), which encompasses long-term expenses such as maintenance, fuel, and depreciation over a vehicle's lifecycle, TTL in automotive sales strictly covers the immediate, out-of-pocket add-ons at purchase.^[56]^[57]

Slang and informal abbreviations

In informal contexts, particularly in texting, social media, and internet culture, TTL most commonly serves as an abbreviation for "Take the L," a phrase meaning to accept defeat, failure, or an unpleasant outcome, such as in sports, arguments, or everyday setbacks.^[58] This usage encourages acknowledging a loss gracefully rather than denying it, often with a tone of resignation or humor.^[59] Other variants of TTL in slang include "Time to Leave," signaling the need to exit a situation or conversation, commonly seen in casual online chats; "Talk to You Later," a shorthand farewell though less frequent than the similar TTYL; and "Thank the Lord," an expression of relief or gratitude in religious or exclamatory contexts.^[58]^[60] These interpretations emerged primarily in digital communication spaces like early internet forums and text messaging. The phrase "Take the L" traces its roots to sports terminology, where "L" denotes a loss, with early documented slang usage appearing around 2003, but it gained traction in the 2010s through hip-hop music and memes.^[59] Originating in American urban slang, possibly from Chicago's cultural scene, it spread virally on platforms like Vine and TikTok after 2015, evolving into a broader internet staple for any form of setback.^[59] In contrast, "Time to Leave" arose in 2000s chat rooms as a quick way to end interactions, reflecting the brevity of early online etiquette.^[61] Examples of TTL in use include texting phrases like "Game over, TTL" after a failed plan or competition, or posting on social media: "Lost the debate—TTL and move on."^[59] Usage varies by generation, with Gen Z favoring "Take the L" in memes and gaming contexts for its ironic edge, while older users might lean toward "Talk to You Later" in more straightforward farewells.^[59] Culturally, TTL as "Take the L" has integrated into emoji combinations (e.g., paired with 😂 or 💀 for humorous losses) and popular abbreviation guides, amplifying its role in viral content, though its abbreviated form is declining in favor of spelled-out phrases in semi-formal writing to avoid ambiguity.^[59]

References

[1]
What Is Transistor-to-Transistor Logic (TTL)? Definition from ...
Jul 21, 2023 · Transistor-to-transistor logic (TTL) is a digital logic design that uses bipolar transistors to switch direct current on and off.
[2]
TTL logic family - HyperPhysics
TTL (Transistor-Transistor Logic) uses bipolar transistors, defines logic 0 as 0V to 0.8V, and is the largest family of digital ICs, requiring +5 volts.
[3]
Digital Logic Gates - Electronics Tutorials
Standard commercially available digital logic gates are available in two basic families or forms, TTL which stands for Transistor-Transistor Logic such as the ...Classification Of Integrated... · Digital Logic States · Basic Ttl Logic Gates
[4]
1963: Standard Logic IC Families Introduced | The Silicon Engine
Thomas Longo led the design of the first TTL family, Sylvania Universal High-level Logic (SUHL) in 1963.
[5]
Fifty years of TTL - Embedded
Jun 16, 2014 · Wikipedia says that although TTL was invented in 1961, TI released the 5400 family of IC's in 1964, and that the 7400 series in plastic came out ...
[6]
The Rise of TTL: How Fairchild Won a Battle But Lost the War
Jul 13, 2015 · Introduced in the early 1960s, TTL found few applications in mainframe computers, the major semiconductor market segment of the time, but ...
[7]
What is Transistor Transistor Logic (TTL) & Its Working - ElProCus
This Article Discusses an Overview of Transistor Transistor Logic (TTL), History, Types, Working, Comparison, Advantages & Its Disadvantages.
[8]
Mastering TTL Logic: A Guide to Digital Circuit Design
Jun 27, 2024 · Transistor-Transistor Logic, or TTL for short, is a foundational technique for designing digital circuits that build logic gates out of bipolar ...
[9]
TTL Logic Levels - SparkFun Learn
TTL is an acronym for Transistor-Transistor Logic. It relies on circuits built from bipolar transistors to achieve switching and maintain logic states.
[10]
Fifty Years of TTL - EE Times
Jun 25, 2014 · Wikipedia says that although TTL was invented in 1961, TI released the 5400 family of IC's in 1964, and that the 7400 series in plastic came out ...Missing: history | Show results with:history
[11]
Understanding Metering and Metering Modes - Photography Life
Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO.
[12]
full aperture metering explanation. - CanonFD FAQL
If we look at the TTL meter in the camera, what it does is simply measure the brightness of the light coming through the lens and takes information about film ...Missing: photography | Show results with:photography
[13]
Through-The-Lens (TTL) Metering - Glass — Photography Community
Through-The-Lens (TTL) metering measures light through the camera lens to set exposure accurately, accounting for filters and lens effects for optimal ...
[14]
Stopped down or full aperture metering – why it still matters for users ...
Feb 9, 2017 · For a single lens reflex camera or a lens manufactured after 1975, full aperture vs stopped down metering is a non issue.
[15]
A Minolta/Sony Alpha Flash Compendium - Flash Metering Modes
TTL-OTF metering is a completely different approach to get correct flash exposure. “TTL” means “Through The Lens”, ie. light is metered through the lens.
[16]
Fundamentals of TTL Strobe Control by Pavel Kolpakov
Sep 6, 2021 · ” OTF stands for “Off-The-Film.” It meant measuring the light reflected from the surface of the photographic film. The sensor for TTL flash ...
[17]
Your Camera's Metering System Explained
Your camera's metering system “reads” the light reflecting from surfaces in front of the lens and reports its findings both in the viewfinder and on the LCD ...
[18]
a historic timeline of the Single Lens Reflex (SLR) camera 1676 ...
Sep 23, 2013 · 1963. Japan. Topcon RE Super – first 35mm SLR with TTL light metering, using internal cadmium sulphide (CdS) photo-resistive cells. Olympus Pen ...<|control11|><|separator|>
[19]
Olympus Pen FT – Half yet double - Photo Thinking Camera Review
May 3, 2025 · In 1966 the Olympus Pen FT (the camera in this article) was brought to market with an uncoupled Through the Lens (TTL) CdS meter and a lower ...Missing: Minolta 1971
[20]
MINOLTA HISTORY - The Sub Club
And by 1966, Minolta had finally "done it". It began production of an SLR with a TTL meter, operating with a fully-automatic aperture and interchangeable ...
[21]
Canon F-1 (Original) Film Camera Review - Analog.Cafe
Sep 3, 2024 · The F-1 was introduced in 1971 ... Canon F-1 is a fully mechanical 35mm film SLR with a built-in TTL match-needle light metering system.
[22]
Debut of Nikon F2 | Camera Chronicle
Nikon F2 Photomic was evolved into Nikon F2 Photomic S in March 1973 by replacing the Photomic finder with the Photomic S finder which adopted the LED (light ...
[23]
Olympus OM-2 MD (1975) - mike eckman dot com
Feb 10, 2017 · The metering system on the OM-2 was so accurate that it allowed for automatic exposures of up to 120 seconds, which is unheard of, even today.
[24]
What is E-TTL II Flash Metering? - SNAPSHOT
Apr 27, 2018 · E-TTL mode, also known as E-TTL autoflash, is the mode where the camera uses information obtained through the lens ("TTL") to calculate how much ...Missing: Nikon Sony Alpha
[25]
Nikon camera TTL History - What is TTL, D-TTL, iTTL
The first Nikon digital models D1 and D2 used the D-TTL system for automatic metered flash, but since then (the last 20 years), the iTTL system is used.
[26]
Open Aperture Metering | Photrio.com Photography Forums
Jul 8, 2020 · The Canon FT QL had stop-down TTL metering in 1966. Canon's full aperture TTL metering cameras came in 1971. They were the F-1 and the FTb.The ...Missing: explanation | Show results with:explanation
[27]
Olympus OM-2 SLR camera - Preface - MIR
The TTL OTF flash metering, in particular, opens up a lot of photographic possibilities which previously involves tedious exposure calculation. The original ...
[28]
View by period - 1955-1969 - Canon Camera Museum
In the 1960s, the Through the Lens (TTL) metering system was identified as the challenge for the SLR cameras. TTL metering determines the optimal exposure for ...
[29]
The Ten Best Mechanical 35mm Film SLRs Ever Made
Jan 11, 2021 · After seven years of shooting classic cameras, we've compiled our list of the ten best mechanical SLRs (plus three honorable mentions).
[30]
Transistor Transistor Logic (TTL) - Digital Logic Circuits - Microsystems
Jan 15, 2024 · The NAND gate is the basic building block of this logic family. ... Figure 1.0 below shows the internal schematic of a standard TTL NAND gate.
[31]
None
### Summary of TTL Fundamentals from SN7400 Datasheet
[32]
[PDF] AN-643 EMI/RFI Board Design (Rev. B) - Texas Instruments
The transient voltage is approximately dV = 0.016 ×. 25Ω = 400 mV, which is equal to the noise immunity level of the TTL logic. A 25Ω (or higher) impedance is.
[33]
SN7400 data sheet, product information and support | TI.com
TI's SN7400 is a 4-ch, 2-input, 4.75-V to 5.25-V bipolar NAND gates. Find parameters, ordering and quality information.
[34]
[PDF] Digital Logic Families: Transistor-Transistor Logic (TTL)
Used extensively in digital calculators, LED displays, and early electronic gaming consoles for logic operations and data manipulation. Industrial Control ...Missing: Altair 8800
[35]
[PDF] Understanding and Interpreting Standard-Logic Data Sheets (Rev. C)
Jun 4, 2016 · LS – Low-Power Schottky Logic. LV – Low-Voltage CMOS Technology. LVC ... tPLH Propagation Delay Time, Low-Level to High-Level Output.
[36]
[PDF] ADVANCED SCHOTTKY (ALS AND AS) LOGIC FAMILIES
22 High- to Low-Level Propagation Delay vs Load Capacitance. 13 ... Table. Title. Page. 1 Typical Performance Characteristics by TTL Series. 2.
[37]
[PDF] SN54/74HCT CMOS LOGIC FAMILY APPLICATIONS AND ...
SN54/74HCT are high-speed CMOS circuits with modified input circuitry for TTL compatibility. They are not for critical applications like life support.
[38]
Understanding Digital Logic ICs — Part 1 | Nuts & Volts Magazine
The most significant differences between the technologies of CMOS and TTL ICs can be seen in their basic inverter/buffer networks, which are used (sometimes ...<|separator|>
[39]
About CMOS, ECL, and TTL Propagation Delay in High Speed PCBs
Apr 23, 2019 · TTL propagation delay is ~33 ns or less, depending on the sub-family. High-speed TTL has propagation delay reaching 6 ns, although this sub- ...Missing: derating | Show results with:derating
[40]
[PDF] Logic Guide (Rev. AB) - Texas Instruments
Standard TTL ... VIH and VIL, which are the minimum switching levels for guaranteed operation. Vt is the approximate switching level and the VOH and VOL levels ...
[41]
https://datatracker.ietf.org/doc/html/rfc8200
[42]
RFC 791 - Internet Protocol - IETF Datatracker
Jul 29, 2020 · The internet protocol provides for transmitting blocks of data called datagrams from sources to destinations, where sources and destinations are hosts ...Missing: origins | Show results with:origins
[43]
[PDF] The Design Philosophy of the DARPA Internet Protocols - MIT
For some goals such as routing, we had mechanisms (e.g. the TTL field) that we could incorporate in the architecture to support the objective. For performance,.
[44]
What Is Time to Live (TTL)? - IBM
Time to live (TTL) is a value that defines the amount of time that a data packet or record should exist on a network, computer or server before it is discarded.Missing: queues | Show results with:queues
[45]
Azure Service Bus - Message expiration (Time to Live)
Dec 2, 2024 · If the message has TTL then this expires-at-utc is computed at the time message is sent and stored.
[46]
RFC 791: Internet Protocol
Fragment Offset This internet header field indicates where in the internet datagram a fragment belongs. GGP Gateway to Gateway Protocol, the protocol used ...
[47]
RFC 8200 - Internet Protocol, Version 6 (IPv6) Specification
This document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460. Status of This Memo This is an Internet Standards Track document.
[48]
Use the Traceroute Command on Operating Systems - Cisco
The traceroute command allows you to determine the path a packet takes in order to get to a destination from a given source by returning the sequence of hops ...
[49]
RFC 2181 - Clarifications to the DNS Specification - IETF Datatracker
RFC 2181 addresses issues with the DNS specification, such as multi-homed server IP addresses, TTLs, zone cuts, SOA records, and valid DNS labels.
[50]
RFC 5082: The Generalized TTL Security Mechanism (GTSM)
The Generalized TTL Security Mechanism (GTSM) is designed to protect a router's IP-based control plane from CPU-utilization based attacks.<|control11|><|separator|>
[51]
RFC 2328 - OSPF Version 2 - IETF Datatracker
This memo documents version 2 of the OSPF protocol. OSPF is a link-state routing protocol. It is designed to be run internal to a single Autonomous System.
[52]
RFC 1112: Host extensions for IP multicasting
This memo specifies the extensions required of a host implementation of the Internet Protocol (IP) to support multicasting.Missing: TTL scoping
[53]
IP Time to Live (TTL) and Hop Limit Basics - Packet Pushers
May 8, 2019 · To ensure IP packets have a limited lifetime on the network all IP packets have an 8 bit Time to Live (IPv4) or Hop Limit (IPv6) header ...Missing: definition origins ARPANET
[54]
When Do You Pay Tax, Title, and License on a Car? - CarsDirect
May 23, 2019 · Tax, title, and license (TTL) fees are collected every time you purchase a vehicle, no matter if it's new or used. When and where you pay ...
[55]
Tax Title and License Calculator - thecalcs
Our TTL calculator computes total vehicle purchase costs by applying your state's sales tax rate to the taxable amount (vehicle price minus trade-in), then ...
[56]
Auto Tax Rates by State (2024) - Policygenius
Feb 7, 2024 · Car sales tax rates fall between 0% to 8.25% depending on the state, with a national average rate of 4.99%. At 8.25%, Nevada has the highest car ...Car tax rate by state · Which states have the highest...Missing: TTL | Show results with:TTL
[57]
Motor Vehicle Titles - Flagler County Tax Collector
Title fees range from $75.75 to $95.75 with options of recording a lien and leaving the office with your new certificate of title in hand. Florida Vehicle ...Motor Vehicle Titles · Florida Vehicle Titles · Out-Of-State Titles
[58]
New Hampshire Car Sales Tax: Everything You Need To Know
Dec 7, 2022 · No. New Hampshire is one of the five states that doesn't collect a general sales tax, including car sales transactions.Missing: TTL | Show results with:TTL
[59]
Licensing Cars and Drivers | National Museum of American History
In 1901, New York became the first state to register automobiles; by 1918 all states required license plates. States were slower to require licenses for drivers ...
[60]
The History of Vehicle Titles - Maggard Information Associates
Jan 30, 2023 · The first vehicle title laws were introduced in the 1920s, with most states requiring that vehicles be registered with the Department of Motor ...
[61]
TTL Meaning & Definition - NoSlang.com
The abbreviation 'TTL' stands for 'total' and is often used in the context of sums, calculations or expenses. This can refer to the total amount of money spent, ...Missing: invoices accounting business
[62]
Total Cost of Ownership: How It's Calculated With Example
Key Takeaways. Total cost of ownership (TCO) includes the purchase price of a particular asset, plus operating costs, over the asset's life span.Missing: TTL | Show results with:TTL
[63]
TTL - Slang/Internet Slang - Acronym Finder
What does TTL stand for? ; TTL, Take the L ; TTL, Thank the Lord ; TTL, Time to Laugh ; TTL · Talk to You Later (text and chat slang; more commonly seen as TTYL).
[64]
What Does "Take the L" Mean, and How Do You Use It?
Sep 1, 2021 · "Take the L" can also be used to describe doing something that you don't want to do. For example, if you're bemoaning to a friend how you have ...
[65]
TTL - What does TTL stand for? The Free Dictionary
Take the L. TTL, Time to Leave. TTL, Tropospheric Transition Layer (atmosphere) ... Talk to You Later (text and chat slang; more commonly seen as TTYL). TTL ...
[66]
What Does Ttl Mean? - Meaning, Uses and More - FluentSlang
The origins of the word/phrase “ttl” are not clear. It is commonly used ... It is an abbreviation that stands for “Time to leave” and is commonly used ...