Scale Expander for 12V Meter (CB21330E)

This circuit was found in a QST from the 1990s. The circuit expands the scale of a 10V instrument to measure 20V.

Telephone Bell (CB25683E)
This additional bell circuit was found in the February 1994 Electronics Now magazine. The...
Delayed Reed Relay (CB12185E)
A delay of a few seconds to a few tens of seconds can be achieved with this circuit found in a...
Single Transistor Alarm Circuit (CB24372E)
This circuit uses a transistor to trigger the alarm from a low quiescent current sensor. The relay...