In this circuit of an old American documentation, the input impedance is the same as the output impedance. The circuit has a sensitivity of 1 Vpp at 75 ohms.
This circuit is from Popular Electronics from the 90's. The circuit discharges the battery with a...
We found this time base circuit in a timer project from the August 1972 Radio Electronics...
This sonic switch, vox or sonic relay uses a Darlington of the time that has a gain of 10,000. The...