Abstract: An electronically controlled coin tester which positions a sample coin in a magnetic field then passes a test coin through a similar magnetic field to create a null in a detector coil sensing the fields. The output of a square wave oscillator is differentiated to generate a spiked signal for exciting the magnetic field. The presence of the test coin is detected by sensing the quality of the null and test coin is accepted in response to the duration of the null. Preferably, a capacitor is charged in the absence of the test coin and discharged in the presence of the test coin and the test coin is accepted in response to the amount of energy stored in the capacitor at the time the null is produced. In addition, a pendulum damper is provided for engaging the test coin prior to its entry into the magnetic field and variably retarding the test coin in response to the coin size.

Abstract: An electronically controlled coin tester which distinguishes between valid and invalid coins by subjecting both the token to be tested (test coin) and a fixed reference coin (sample coin) to similar magnetic fields and evaluating the quality of any null signals created by their combined output. A selectively shiftable coin holder is provided which serves to allow replacement of the sample coin as well as to provide a guiding ramp for the test coin which can be selectively set at various inclines dependant upon the size of the coins desired to be tested. The present device may optionally include a pendulum damper which will slow the movement of the test coin as its travels along the guiding ramp, and/or an antistringing device which prevents the removal of a coin from the coin box after acceptance.