This circuit is from American documentation from 1970. It can be designed with a BC558 and for the operational, we can use equivalents. The FET can be the BF245.
This circuit was found in Motorola documentation from 1968. SCRs can be modern equivalents and the...
We found this circuit in a Popular Electronics of the 90s. Its purpose is to detect when it locks...
This circuit was obtained from Signetics documentation from the 1980s. The circuit can be...