In 1973, LSI chips were not readily or cheaply available, so all the multiplexing and logic were done using chips that consisted of four two-input TTL NAND gates, which resulted in excessive power consumption.

Standard TTL NAND with a " totem-pole " output stage, one of four in 7400

* TTL NAND and AND gates from Lessons In Electric Circuits by Tony Kuphaldt

Before PALs were introduced, designers of digital logic circuits would use small-scale integration ( SSI ) components, such as those in the 7400 series TTL ( transistor-transistor logic ) family ; the 7400 family included a variety of logic building blocks, such as gates ( NOT, NAND, NOR, AND, OR ), multiplexers ( MUXes ) and demultiplexers ( DEMUXes ), flip flops ( D-type, JK, etc.

TTL manufacturers offered a wide range of logic gate, flip-flops, counters, and other circuits.

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

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.

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.

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:

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

It was built from three boards of ECL gate array chips ( with TTL pinout ).

The TTL logic gate, which was the electronics industry standard for two decades, was invented by TRW's James L. Buie in 1961.

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 ).

The TTL output stage is a rather complicated push – pull circuit known as a `` totem-pole output ( the transistors, diode, and resistor in the right-most slice of this TTL logic gate circuit ).

The PALM processor was an entire circuit board containing 13 square metal-can bipolar gate arrays, 3 conventional DIP transistor-transistor logic ( TTL ) parts and 1 round metal can part.

Present-day " building block " logic gate ICs are based on the ECL, TTL, CMOS, and BiCMOS families.

Since the transistors of a standard TTL gate are saturated switches, minority carrier storage time in each junction limits the switching speed of the device.

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

Image: Nikon-ftn-400. jpg | Nikon FTN with interchangeable photomic TTL metering prism

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

In addition, Commodore made the drive's controller board smaller and having a lower chip count than the early 1541s ( which had a large PCB with dozens of TTL chips running the length of the case ).

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.

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.

Transistor-transistor logic ( TTL ) then supplanted DTL with the observation that one transistor could do the job of two diodes even more quickly, using only half the space.

Initially a 32-bit TTL processor in conjunction with supporting microcode implemented the programmer-visible architecture.

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.

A dedicated voltage comparator chip such as LM339 is designed to interface with a digital logic interface ( to a TTL or a CMOS ).

The first SLR cameras with internal (“ through-the-lens ” or “ TTL ”) meters ( e. g., the Pentax Spotmatic ) required that the lens be stopped down to the working aperture when taking a meter reading.

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

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.

After introduction in integrated circuit form in 1963 by Sylvania, TTL integrated circuits were manufactured by several semiconductor companies, with the 7400 series by Texas Instruments becoming particularly popular.

Several variations from the original bipolar TTL concept were developed, giving circuits with higher speed or lower power dissipation to allow optimization of a design.

Successors to the original bipolar TTL logic often are interchangeable in function with the original circuits, but with improved speed or lower power dissipation.

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.

The term " TTL " is applied to many successive generations of bipolar logic, with gradual improvements in speed and power consumption over about two decades.

The main disadvantage of TTL with a simple output stage is the relatively high output resistance at output logical " 1 " that is completely determined by the output collector resistor.

The main advantage of TTL with a " totem-pole " output stage is the low output resistance at output logical " 1 ".

Standard TTL circuits operate with a 5-volt power supply.

For example, the HP 59501 Power Supply Programmer and HP 59306A Relay Actuator were both relatively simple HP-IB peripherals implemented only in TTL logic, using no microprocessor.

Another more advanced method is to attach a TTL to the modem's RS-232 adapter, and get access to the modem's console directly to make it download new firmware, which can then be configured via a simple web interface.