Resistor-Transistor Logic was an early form of logic used in the 1950's and early 1960's.
RTL was made from discrete transistors and resistors and manufactured on printed circuit
boards with several gates per board. These boards were plugged into board sockets with
wiring on the socket pins determining the system function. RTL was a big improvement
over vacuum tube technology previously used, requiring less than one quarter the space
and one tenth the power dissipation. RTL was superceded in the 1960's by DiodeTransistor
Logic and then Transistor-Transistor Logic, DTL and TTL respectively. DTL
was initially made with discrete transistors and resistors before being integrated onto
silicon. One early form of DTL, used by IBM Corp in the 360 family of computers, was
really a hybrid technology. Transistor and diode chips were glued to a ceramic substrate
and aluminum resistor paste was deposited on the substrate to make resistors. Finally the
ceramic base and components were hermetically sealed in an aluminum can. This family
was used extensively in IBM products in the middle to late 1960's. While this family was
not a true integrated circuit, it was very successful and was less expensive than true
integrated circuits for several years. By the early 1970's integrated circuits became quite
common and DTL gave way to TTL which was more appropriate to integrated circuit
technology.