Off-hook Telephone Indicator (CB5994E)

This circuit was found in a 1980s US publication. It indicates when the phone is off-hook by triggering an indicator.

| Clique na imagem para ampliar |

Signal Tracer with MW Radio (CB20509)
In the figure we have a simple signal tracer circuit to be coupled to the volume control of an AM...
Flip Flop Toggle (CB24436E)
This circuit was found in documentation from the 90s, using components from that time. The...
Battery Desulfator Charger (CB19386E)
This circuit, obtained from old documentation, allows the recovery of sulfated batteries. The...