Signal Tracer and Capacitor Tester (T1241E)

This mains powered two-in-one instrument was found in a Radio Craft from March 1948. The headphone must be high impedance.

1 kHz Active Band Pass Filter RC4558 (CB19782E)
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
Miniature 1 Cell Transmitter (CB19437E)
This circuit works with only one battery, providing a range of a few tens of meters. We found it...
Analog Multimeter (CB11829E)
This circuit from the 40's is a conventional analog multimeter with several scales. Its accuracy will...