This is the receiver for the previous transmitter. The microphone is of the high impedance ultrasonic type. The circuit activates a relay. The operational amplifier supports equivalent.
Being able to operate with frequencies up to 100 kHz, this circuit was found in a 90’s...
The integrated circuit used in this filter is not very common today, but the reader can use...
This circuit doubles the frequency of signals from 10 to 50 MHz. We found it in a 1969 Electronic...