Datasheet of This battery powered intercom was found on a January 1947 Radio Craft. |The circuit is 4-way but can be modified by changing the key.
This circuit is from the 1994 Linear Applications Handbook. The operational circuit can be...
This circuit is suggested by National Semiconductor (now Texas) in an old manual. The circuit...
With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a...
