This amplifier with the LM1098 and LM101 by Motorola from a 1990 manual can be designed with more modern operations. The bandpass for small signals is 3.5 MHz and the power range is 250 kHz.
The values of the capacitance between output A and ground can be programmed digitally in 18 steps...
This circuit is the traditional 555 oscillator that produces a hum in the piezoelectric...
This circuit activates an output, which can be a lock, only when a card containing the programmed code...