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.

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

TTL circuits simplified design of systems compared to earlier logic families, offering superior speed to resistor – transistor logic ( RTL ) and easier design layout than emitter-coupled logic ( ECL ).

TTL became popular with electronic systems designers after Texas Instruments introduced the 5400 series of ICs, with military temperature range, in 1964 and the later 7400 series, specified over a narrower range, and with inexpensive plastic packages in 1966.

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.

This effect is less marked for TTL systems, which is one reason why they maintained a speed advantage over CMOS for many years.

In this way, TTL delivers some of the benefits associated with active four-wheel steering systems while being lighter and mechanically less complicated than such systems.

Older systems such as TTL used 5 volts, newer computers typically use 3. 3 volts ( LV-TTL ) or even 1. 8 volts.

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

Nevertheless, for most applications analogue TTL flash exposure metering was more advanced and accurate than systems used previously and permitted far more flexibility-with bounced flash exposures in particular being more accurate than manually calculated equivalents.

Like most integrated circuits of the period 1965 – 1990, TTL devices were usually packaged in through-hole, dual in-line packages with between 14 and 24 lead wires, usually made of epoxy plastic ( PDIP ) or sometimes of ceramic ( CDIP ).

Several manufacturers now supply CMOS logic equivalents with TTL-compatible input and output levels, usually bearing part numbers similar to the equivalent TTL component and with the same pinouts.

As integrated circuits in the 7400 series were made in different technologies, usually compatibility was retained with the original TTL logic levels and power supply voltages.

Push – pull outputs are present in TTL and CMOS digital logic circuits and in some types of amplifiers, and are usually realized as a complementary pair of transistors, one dissipating or sinking current from the load to ground or a negative power supply, and the other supplying or sourcing current to the load from a positive power supply.

Nameservers may also have a TTL set for NXDOMAIN ( acknowledgment that a domain does not exist ); but they are generally short in duration ( three hours at most ).

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

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.

Consequently, CMOS devices do not produce as much waste heat as other forms of logic, for example transistor-transistor logic ( TTL ) or NMOS logic, which normally have some standing current even when not changing state.

If the exposure flash is fired at approximately this interval after the TTL measuring flash, people will be squinting or have their eyes shut.

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 ).

Many parts in the CMOS HC, AC, and FC families are also offered in " T " versions ( HCT, ACT, and FCT ) which have input thresholds that are compatible with both TTL and 3. 3 V CMOS signals.

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.

* a few low-power TTL devices ( e. g. 74L86, 74L9 and 74L95 ) have a different pin-out than the regular ( or even 74LS ) series part.

Ethernet does not have a time to live ( TTL ) field in its frame header, so loop avoidance must be arranged by other means.

Since the Kenbak-1 was invented before the first microprocessor, the machine didn't have a one-chip CPU but instead was based purely on discrete TTL chips.

The FG was also Nippon Kogaku ’ s first amateur level SLR to have through-the-lens TTL off-the-film ( OTF ) electronic flash automation.

The time for which a resolver caches a DNS response is determined by a value called the time to live ( TTL ) associated with every record.

RFC 1912 conveys basic rules for determining appropriate TTL values.

Some resolvers may override TTL values, as the protocol supports caching for up to 68 years or no caching at all.

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.

The tracert ( traceroute ), Pathping commands are implemented by transmitting UDP datagrams with specially set IP TTL header fields, and looking for ICMP Time to live exceeded in transit ( above ) and " Destination unreachable " messages generated in response.

When a caching ( recursive ) nameserver queries the authoritative nameserver for a resource record, it will cache that record for the time ( in seconds ) specified by the TTL.

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.

An older common TTL value for DNS was 86400 seconds, which is 24 hours.

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.

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

The circuit diagram for a 4 bit Transistor-transistor logic | TTL counter, a type of state machine

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.

TTL also became important because its low cost made digital techniques economically practical for tasks previously done by analog methods.

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 maximum value of this current is about 1. 6 mA for a standard TTL gate.

TTL outputs are typically restricted to narrower limits of between 0 V and 0. 4 V for a " low " and between 2. 6 V and 5 V for a " high ", providing 0. 4V of noise immunity.