We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
This integrating circuit multiplies the time that can be obtained with a 555 timer. We find it in...
This circuit was found in a 1967 Ferranti documentation. It takes the transistor to the conduction...
This circuit for receiving or transmitting low power was found in old American documentation. It is...