This circuit is better than the previous one in that the control is isolated by a transformer. The transformer has 110 or 220 V primary and 6.3 to 12 V secondary with 200 to 500 mA current.
This circuit, from a 1987 documentation, is for the CB3817E transmitter. Connected to the handset...
This circuit is from a 1975 technical documentation on filters. The FET can be a BF245 and the...
This circuit uses a sensitive 9V relay but can be built with 6 or 12V relays by changing the power...