This circuit was obtained from American documentation from 1966. It triggers when the two input voltages are within a pre-established range. The circuit can be mounted with modern transistors.
This circuit for tape recorders was found in the February 1990 Radio Electronics magazine. The...
This Signetics circuit uses a double 555 (556) to generate tone bursts at frequencies determined by...
Found in an American documentation from 1969, this astounding circuitry makes a relay operate on 3 Hz...