| 摘要 |
An electronic tone ringer for use in a telephone instrument to respond to ringing currents to generate an output tone electronically is described. A controlled breakdown rectifier bridge is placed across the input line to produce a d.c. output in response to ring input. The d.c. output is fed to an oscillator to produce a signal which is fed to a piezo-electric transducer to produce output tones. A number of safeguards are built into the circuit to prevent random noises from being fed to the oscillator. Further, the controlled breakdown bridge provides voltage clamp action to prevent spikes of voltage from damaging the circuit.
|
