Ring tone generator (CB9301E)

Found in Elektor Electronics from the 90s, this circuit produces the tone of 1 750 Hz for calling VHF relay stations used by radio amateurs.

| Clique na imagem para ampliar |

Sine to Square Converter (CB6586E)
Found in American documentation this circuit uses transistors of the time. The circuit can be made...
1 W Amplifier (CB6295E)
The TAA300 integrated circuit is not common today. In fact, the circuit shown is from a Dutch...
Rain Alarm or Door Bell (CB5369E)
This circuit was found in a 1980s documentation. Q1 and Q2 can be BC548 and SCR a TIC106. The...