This circuit was found in a 1981 publication and consists of an interesting handicraft game. The complete circuit of the game is shown in the figure and operates as follows: the player must try to pass the ring through the tortuous wire without allowing one to touch the other. If this happens, the circuit trips by closing the relay contact, which then switches the visual indication from green to red. If this happens a negative point must be counted for the player or else, he must be disqualified to give another player the opportunity. The circuit is reset on each trip by pressing switch S1 in parallel with the SCR. The circuit is supplied with a voltage of 6 or 12 V and the relay must be chosen to close with this value. It should be noted that the small voltage-drop in the order of 2 V that occurs in the SCR while driving must be considered in the relay's sensitivity.
