MORE ACCURATE TIME FROM THE HEATHKIT MOST ACCURATE CLOCK

The addition of an auxiliary circuit to the Heathkit GC-1000 clock is described. The circuit, which consists of two integrated circuits, two resistors, and three capacitors, will supply a more accurate timing pulse to the computer. The circuit contains two input signals and produces one output; the inputs are multiplexed seven-digit displays (two digits for hour, minute, and second, and one for tenths of a second) and the output appears as a string of about 10 low-going pulses about 1.25 ms in duration. Low pass filters (R1 and C1) are utilized to eliminate extraneous pulses. The materials and procedures for attaching the circuit to the clock are examined. The software for the data set ready signal, and the method for accurate timing of data collection are discussed. The accuracy of the clock is evaluated and it is observed that the circuit improves the correct time provided by the clock from + or - 29 ms to + or - 5 ms.