Relative impedance meter (CB7487E)

Found in a 1960 Sylvania manual, this circuit can be implemented with a modern equivalent transistor like the BC558.

Variable Voltage Controlled Attenuator (CB4236E)
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
741 Oscillator (MSB009)
This circuit produces a square wave signal with the frequency determinated by R1 and C1. The upper limit...
10 Gain Amplifier LM3900 (CB5042E)
In the figure we have the circuit of an amplifier for alternating signals with 10 times gain,...