Telephone in use indicator (CB9467E)

We found this circuit in a Hands-On Electroncs from the 90s. The circuit uses an LED indicator. Diodes are general purpose types.

| Clique na imagem para ampliar |

Multiplexed AD Converter (CB9023E)
This 8-channel converter was found in a 1970s American documentation. The integrated circuits used are...
General Purpose Phone Amplifier (CB974E)
We find the original version of this circuit in an English publication (1986). It is a...
Long Range Telegraph (CB11949E)
This experimental telegraphic communication system can have wires connecting to the handset of...