Fifty years ago, this British family stayed connected thanks to this three-transistor (one germanium, two silicon) intercom, from the May 1973 issue of Everyday Electronics. The set was tested with a range of fifty feet, and the author believed that it would perform well over a much longer connection. Similar commercial units were available, but the cost of materials (about three pounds) of this project was considerably lower.

The master unit used a spring-loaded push to talk switch.