| 摘要 |
<p>The specification describes a tone generator for producing an audible sound for a predetermined time period in response to the occurrence of one or more predetermined conditions. The tone generator comprises a diaphragm mounted within a resonant sound cavity that is activated by an electromagnetic assembly which is in turn driven by the output signal from an oscillator circuit. The circuit utilizes a triple positive temperature coefficient (PTC) resistor, with one resistor used as a primary heating element, another as a switching element for a lamp, and the third as a logic switching element for the logic signal that times the tone generator. The control logic and timing circuit is adapted to produce the proper timed logic signal despite the absence of a lamp in the circuit, or a lamp failure.</p> |
