Shift Registers as Delay Lines (was Delay lines in TV sets)

Tom Watson wrote: A lot of early MOS shift registers were developed specifically for use in electronic calculators, as solid-state replacements for magnetic core memory or magnetostrictive delay lines. Since most all electronic calculators in the mid-'60's through the late 70's operated in BCD or some alternate four (or sometimes five)-bit representation of decimal digits, the shift registers were usually made with a number of stages that was a multiple of four or five, with a few extra bits here and there for timing and synchronization. That's why many of these devices as an unusual number of stages. In some calculators from the late '60's, as IC logic had pretty much replaced discrete transistor designs, there were different versions of the same machine, earlier machines which used a magnetostrictive delay line, and "updated" versions which dispensed with the delay line, and replaced it with a number of MOS IC shift register devices. Functionally, the machines were identical. As far as the digital logic section of the machine went, also identical. The only real changes were the removal of the read amplifier and write driver for the delay line, and replacement with some simple level-shifting and power supply circuitry to properly drive the shift register chain. Rick Bensene The Old Calculator Museum http://oldcalculatormuseum.com