This assembly is from 1957 from a Raytheon manual, but can be modernized using a BC548, 6 V power supply and common 100 mA relays.
This amplifier was suggested by the Texas Instruments linear applications manual of the 90s....
This circuit appears elsewhere on the site. The circuit shown is from an American 1980s...
We found this circuit in Texas Instruments' Linear Circuits Applications. In the original it is...