If you need to liven up Junior’s next party, you can put together this circuit for a fun game of “hunt the bleeper,” as described in the November 1972 issue of Practical Wireless.

The magazine noted that British children love noise, and this is equally true on this side of the Atlantic. The beeper, which draws only 600 microamps, puts out a high pitched tone at a low level. The device was to be hidden, and the children would be split into two teams to find it. There were two strategies available: They could concentrate on finding the device, or they could make so much noise to keep the other side from hearing it.

The cost was said to be 50 pence, which didn’t include the case, which was one of the then-ubiquitous 35mm film can, which was deemed to be free. Even though they’re no longer free, like everything else, you can find them on Amazon.

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