Audio Frequency Counter Program for the Timex/Sinclair ZX81

This program will run with as little as 1K of RAM and will allow frequency measurements of up to 28,500 Hz. This is useful for tuning RTTY tone generators, electronic musical instruments, tone encoders, and for calibrating audio generators. The audio signal is fed to the computer’s earphone jack, and the frequency is displayed to the nearest Hz on the screen. Carol F. Milazzo was formerly Charles F. Milazzo.