Audio stage for radios (CB20511E)

This circuit for experimental radios and other applications is from a documentation from the 50's. The original transistors used are germanium.

CB20511E

8 Bit DA Converter (CB5172E)
This circuit was found in an American 80s circuit manual. The components used are unusual. The...
Amplifier for Telephone Pickup (CB988E)
The purpose of this circuit is to amplify the signal of a phone pickup and to be able to reproduce the...
Phone Status Monitor (CB5977E)
We found this circuit in an old documentation, but the components used offer no difficulty in obtaining...