Quick answer (CB20960E)

We found this game for two competitors in a Popular Electronics from the 80's. The circuit can be powered by voltages from 6 to 12 V.

Optical Receiver Shield (CB19865E)
Originally this circuit was indicated to be used in a garage door control, but it can be modified for...
400 Hz 741 Oscillator (CB17028E)
This conventional oscillator with the 741 can be precisely adjusted to produce a 400 Hz signal. The...
Variable voltage regulator (CB21192E)
This current-limited circuit was found in a Popular Electronics from the 90's. ...