This circuit was found in a 1975 documentation. Current general-purpose transistors can be used, and the power is supplied with relatively high voltage. The gain is 30 dB.
This timer activates a relay after a time interval of up to 15 minutes has elapsed, starting from...
This circuit, which can be used on an optical link, is suggested by the Texas Instruments...
This circuit uses an MW radio tuned to around 540 kHz to detect atmospheric signals, for example, from...