Test initiating apparatus for appliances having self-diagnostic testing

Abstract

A test initiating device connectible to the power cord of an electronically controlled appliance for initiating appliance operation in either a normal operating mode or a self-diagnostic test mode. When so connected the test device is selectively switchable between a first state in which the device is operative to suppress power signal half cycles of one polarity and a second state in which the power signal from the power supply is coupled to the appliance control circuit essentially unchanged. The appliance control circuit includes circuitry operative to generate interrupt pulses marking the pulsations of the power signal applied to the control circuit. Logic circuitry monitors the pulse rate of these interrupt pulses. If a pulse rate different from the corresponding to the normal power supply frequency is detected when the appliance is operating in its start-up mode, signifying the test device is in its first state, the self-diagnostic test mode is initiated, otherwise operation in the normal mode is initiated.