This is the receiver for the previous circuit, also found in 90s Radio Electronics. The circuit operates at 2.25 MHz, detecting variations in signal frequency due to the Doppler effect.
This circuit detects light variations using two LDRs as sensors. Operational amplifiers and...
The circuit shown consists of a power stage for relay excitation. 2N3053 can be a BD135 and 2N406...
This circuit was found in Mullard's 1960s transistor manual. The circuit uses germanium...