* The TTL field of IPv4 has been renamed to Hop Limit, reflecting the fact that routers are no longer expected to compute the time a packet has spent in a queue.

Frequently starting with a value like 128 ( Windows ) or 64 ( Linux ), routers decrement this and discard a packet when the TTL value has reached zero, returning the ICMP error message ICMP Time Exceeded.

If a stub resolver queries the caching nameserver for the same record before the TTL has expired, the caching server will simply reply with the already cached resource record rather than retrieve it from the authoritative nameserver again.

Since the invention of the “ solid state ” transistor in the 1950s and the TTL ( transistor-transistor logic ) that led to the development of the IC ( integrated circuit ) in the 1960s the growth in the field of electronics has been phenomenal.

Compared to contemporary ECL circuits, TTL uses less power and has easier design rules but is substantially slower.

The TTL " totem-pole " output structure often has a momentary overlap when both the upper and lower transistors are conducting, resulting in a substantial pulse of current drawn from the power supply.

Variations of and successors to the basic TTL family, which has a typical gate propagation delay of 10ns and a power dissipation of 10 mW per gate, for a power – delay product ( PDP ) or switching energy of about 100 pJ, include:

V < sub > CC </ sub > and Ground are carryovers from TTL logic and that nomenclature has been retained with the introduction of the 54C / 74C line of CMOS.

TTL introduced a new brew, Taiwan Beer Gold Medal, by the end of its first year and has since introduced three more brews: Taiwan Beer Draft ( another lager, for sale in restaurants ) and two malt beers under the Mine label ( Amber and Dark ).

Any and all signals inside a device that has RS232 connectivity are always TTL level ( 0 and 5V or 0 and 3. 3V or 0 and 3v ) internally and conversion to and from RS232 is the last thing outgoing data does, or the first thing incoming data does.

TTL has changed significantly over the years, with newer versions replacing the older types.

They form a replacement for TTL, although HCT is slower than original TTL ( HC logic has about the same speed as original TTL ).

The shutter dial of the M6 TTL is reversed from previous models, turning in the same direction as the light meter arrows in the viewfinder ; this feature has continued in the M7, M8, and M9, but not the MP, which returned to the older, smaller diameter, opposite direction shutter speed dial.

This switch in the TTL approach has shifted its emphasis more towards BTL.

Each node, upon receiving a RouteRequest packet, rebroadcasts the packet to its neighbors if it has not forwarded it already, provided that the node is not the destination node and that the packet ’ s time to live ( TTL ) counter has not been exceeded.

It has a voltage swing between 0. 4 volts and 1. 2 volts — much lower than that used in TTL and CMOS logic — and symmetrical parallel resistive termination.

In the early days of large-scale IC development, a prototype of a new large-scale integrated circuit might have been developed using TTL chips on several circuit boards, before committing to manufacture of the target device in IC form.

However, TTL metering systems have been incorporated into other types of cameras.

The value of the MINIMUM field of the SOA record and the TTL of the SOA itself is used to establish the TTL for the negative answer.

In 1973, the KA10 was replaced by the KI10, which used TTL SSI.

Later systems ( the PDP-8 / I and / L, the PDP-8 / E, / F, and / M, and the PDP-8 / A ) returned to a faster, fully parallel implementation but used much less-expensive TTL MSI logic.

This first implementation of the Pentium used a traditional 5 Volt power supply ( descended from the usual TTL logic compatibility requirements ).

In computing applications, TTL is used to improve performance of caching or improve privacy.

* Gnutella TTL and Hops header values used for preventing loops and monitoring of network topology

TTL is notable for being a widespread integrated circuit ( IC ) family used in many applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, synthesizers, etc.

The designation TTL is sometimes used to mean TTL-compatible logic levels, even when not associated directly with TTL integrated circuits, for example as a label on the inputs and outputs of electronic instruments.

At least one manufacturer, IBM, produced non-compatible TTL circuits for its own use ; IBM used the technology in the IBM System / 38, IBM 4300, and IBM 3081.

The Kenbak-1, ancestor to the first personal computers, used TTL for its CPU instead of a microprocessor chip, which was not available in 1971.

The 1973 Xerox Alto and 1981 Star workstations, which introduced the graphical user interface, used TTL circuits integrated at the level of ALUs and bitslices, respectively.

In some cases ( e. g., when the output of a TTL logic gate needs to be used for driving the input of a CMOS gate ), the voltage level of the " totem-pole " output stage at output logical " 1 " can be increased up to V < sub > CC </ sub > by connecting an external resistor between the V < sub > 3 </ sub > collector and the positive rail.

Although vendors uniformly marketed these various product lines as TTL with Schottky diodes, some of the underlying circuits, such as used in the LS family, could rather be considered DTL.

* Schottky TTL ( S ), introduced in 1969, which used Schottky diode clamps at gate inputs to prevent charge storage and improve switching time.

* Low-power Schottky TTL ( LS ) – used the higher resistance values of low-power TTL and the Schottky diodes to provide a good combination of speed ( 9. 5ns ) and reduced power consumption ( 2 mW ), and PDP of about 20 pJ.

Probably the most common type of TTL, these were used as glue logic in microcomputers, essentially replacing the former H, L, and S sub-families.

TTL inverters can also be used in crystal oscillators where their analog amplification ability is significant.

While it contains no microprocessor, it used the 4004 programming instruction set and its custom TTL was the basis for the Intel 8008, and for practical purposes the system behaves approximately as if it contains an 8008.

* Bipolar junction transistor ( used in TTL and ECL ) — very fast but consumes a lot of power

An external TTL register was often used for sequential designs such as state machines.

Power supplies on the bus were unregulated + 8 V and ± 18 V, designed to be regulated on the cards to + 5 V ( used by TTL ) and ± 12 V ( typically used on RS-232 lines or disk drive motors ).

The TTL field is set by the sender of the datagram, and reduced by every router on the route to its destination.

The purpose of the TTL field is to avoid a situation in which an undeliverable datagram keeps circulating on an Internet system, and such a system eventually becoming swamped by such " immortals ".

In practice, the TTL field is reduced by one on every hop.

A TTL value of 86400 would mean that, if a DNS record was changed on the authoritative nameserver, DNS servers around the world could still be showing the old value from their cache for up to 24 hours after the change.

Newer DNS methods that are part of a DR ( Disaster Recovery ) system may have some records deliberately set extremely low on TTL.

TTL values are " per record " and setting this value on specific records is normally honored automatically by all standard DNS systems world-wide.

A Motorola 68000-based computer with various TTL chips mounted on protoboard s.

Standardization of the TTL levels was so ubiquitous that complex circuit boards often contained TTL chips made by many different manufacturers selected for availability and cost, compatibility being assured ; two circuit board units off the same assembly line on different successive days or weeks might have a different mix of brands of chips in the same positions on the board ; repair was possible with chips manufactured years ( sometimes over a decade ) later than original components.

TTL is particularly well suited to bipolar integrated circuits because additional inputs to a gate merely required additional emitters on a shared base region of the input transistor.

As microprocessors became more functional, TTL devices became important for " glue logic " applications, such as fast bus drivers on a motherboard, which tie together the function blocks realized in VLSI elements.

A short TTL on the A-record helps to ensure traffic is quickly diverted when a server goes down.

Unlike the TTL connectors used in the early days of home computing and game consoles ( most notably the DE-9 connector originally found on the Atari VCS, which was the de facto standard on other systems ) the game port is analog rather than digital, relying on some form of analog-to-digital converter ( ADC ) to interpret joystick movements.

Going on these figures alone TTL logic gates are limited to perhaps 2 to 10, depending on the type of gate, while CMOS gates have DC fan-outs that are generally far higher than is likely to occur in practical circuits ( e. g. using NXP Semiconductor specifications for their HEF4000 series CMOS chips at 25 ° C and 15 V gives a fan-out of 34 thousand ).