This two-transistor circuit is from a December 1964 Radio Electronics. Modern transistors can be tested. The headphone must be high impedance or crystal with a 2k2 resistor in parallel.
This simple circuit, obtained from a Radio Shack documentation, tests transistors and diodes. The...
This simple circuit is intended to test integrated circuits 555 and 741 in 8-pin DIL enclosures. In both...
This is a circuit for receiving signals from the previous transmitter. The circuit uses a common...