This circuit is from an American manual from 1975. The transistors are types of the time, but equivalents can be used, as well as the relay that can be according to the supply voltage.
This is a bridge for the measurement of low value resistances and high values too. The circuit...
This inverter bistable buffer circuit was obtained in a Hands On of the 90's. Next to the circuit we...
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...