Make Pt1549
How to tap a phone – Mechanix Illustrated, March 1957 – fun for the whole family.

THERE are many ways to tap a phone; most of them against the law. Our little gadget, however, is quite legal and can be used to great advantage at home or in the office.

Basically, the unit consists of a pickup coil, an amplifier and a speaker. The pickup coil is placed under, or near, any transformer-type telephone without being in physical contact with it. As the electrical currents pass through the phone, part of the energy is induced into the pickup coil. This energy is fed into the amplifier where it is amplified to the point where it will operate the loudspeaker, enabling everyone within range to hear what is being said at the other end of the telephone line. This will come in handy when some relative is calling long-distance; your whole family can hear what he is saying. Or, in the office, the whole staff can hear a salesman’s report. There are other uses for the pickup, limited only by your own imagination.