Delay Line Memory (Was: Australian ex-DEC Director has large museum in his home)

Delay lines were used a lot in early electronic calculators from the around 1963 through the early 1970's, by which time MOS integrated circuits (first shift registers, then RAM) took over. Delay lines were used extensively in early electronic calculators by Olivetti, Canon, Friden, and Sony, among others. Typically the delay line was used to store the working registers of the calculator, with the data continuously circulating through the delay line and the arithmetic/display logic. Most of the delay lines used in calculators were of the magnetostrictive type, which used thin tapes of nickel (which contract when subjected to a magnetic field), that impart torque twists into a special wire that served as the delay medium. This wire was strung in a spiral, with lengths ranging up to around 50 feet. Magnetostrictive transducers were affixed to each end of the wire, with one end being the transmitter, and the other the receiver. Capacity of the delay line was a function of the length of the loops of wire, and the data rate pushed through the delay line. In the Friden 130, the first production calculator to use a delay line, the delay line wire is about 50 feet long, and the delay is about 5ms, with 480 "bits" of information stored in the delay line. Typically, delay line memories in calculator implementations max out at around 1500 bits of storage. Programmable calculators, like the Monroe EPIC 2000/3000, the Olivetti Programma 101 and follow-on machines, and some Canon programmables had the highest capacity delay lines since the line needed to store both the working registers of the calculator, as well as the user's stored program. In the case of the Monroe EPIC 2000/3000, two delay lines were used (housed in the same enclosure), one for working register storage, and the other for program storage. Rick Bensene The Old Calculator Museum http://oldcalculatormuseum.com