This circuit is from a 1947 Radio Electronics. The 4-tube circuit is battery powered and uses a crystal phone.
The circuit shown is from Motorola's Linear Databook published in 1990. As the CI is uncommon...
We found this circuit in a 1997 documentation. It can be used in any common 12 V source and has...
Using a CA3059 this circuit was found in the July 1995 Electronics Now magazine. The triac must be...