1971 · Integrated Timer Circuit · Work 861 of 1,871
A kitchen table in a house in California at night, in the foreground a single tiny oblong block of plain smooth unmarked matt black plastic ten millimetres long, a small half-round notch at one end with a round dimple beside it, four short tin-silver legs bent down along each side, behind it a breadboard with coloured jumper wires, a large sheet of graph paper with fine pencil lines of a circuit lying at a flat angle and soft in focus, a sheet of deep red translucent film with a craft knife on it, a coffee mug, a hand in a checked flannel sleeve, the cone of a desk lamp from the left.
What it was used for
The 555 is an integrated-circuit timer. In June 1973 Electronics wrote that the commercial versions were intended to compete with mechanical and electromechanical timers, and that with demand exceeding supply business was now quite brisk. In the same issue the magazine printed circuits sent in by practising engineers, among them a car burglar alarm built from 2 timers by Michael L. Harvey of Ropel Corp., El Segundo. Hans Camenzind designed the part as a freelance consultant for Signetics: the company paid 1200 dollars a month for a year and lent him equipment it did not need, having just lost half its engineers. The launch price was 75 cents in quantities of 100. For 1973 Electronics gives sales of all IC timers as upward of 7 to 8 million units a year.
What was new
In his own book Camenzind writes that timers at the time were put together from an op-amp or comparator and a few discrete components, including a Zener diode or two. The design jump was the pin count: his first version needed 9 pins, while the packages available had 8 or 14. Only when he dropped the voltage-to-current converter and charged the capacitor through a resistor did he reach 8 pins - and the timing stayed independent of supply voltage, so the circuit was smaller and more accurate at once. The basic circuit came from the Signetics 566, a voltage-controlled oscillator that grew out of Camenzind's phase-locked-loop work. The barb: there is no patent. Camenzind says Signetics did not want to apply for one, because enforcing it would have brought Fairchild back with its own patents; within six months to a year National and Fairchild had it too.
What the sources leave open: In the 1972 Signetics data book the 555 page is headed as advanced information on a new product, and in the 22 Electronics issues of 1971 available in the archive the part does not appear; the first record is 8 May 1972. Design and prototype therefore belong to 1971, the market to 1972. The component count is given as 23 transistors and 15 or 16 resistors. The figure of 1 billion units a year is the designer's estimate, not a market survey.