Tone-ringing circuits and methods for telephone sets

A tone-ringing circuit for a telephone set having a receiver in the telephone handset and a set of line-switch contacts, which circuit is powered solely by a low-frequency ringing signal from the central office, the circuit comprising:

• an oscillator circuit including an I-C timer chip of the type having input pins, a high-frequency output pin, and a reset pin for disabling the high-frequency output;
• means for rectifying an incoming low frequency ringing signal from the central office and for applying the rectified signal to the oscillator input pins whenever a set of telephone line switch contacts are in the on-hook state;
• means for connecting the high-frequency output to the telephone receiver whenever the line-switch contacts are on-hook so that the high-frequency output operates the receiver as the transducer for the tone ringer;
• and
• means, connected to the reset pin of the chip, for disabling the chip from producing the high-frequency output to the receiver whenever the handset has been lifted from the cradle and the line-switch contacts are thereafter closed, so as to preclude the possibility of a user being rung in the ear.

A method of ringing a telephone set having a receiver in the telephone handset and a set of line switch contacts, wherein the ringing circuit is powered solely by a low-frequency ringing signal from the central office, which method comprises:

• (a) rectifying an incoming low-frequency ringing signal from the central office whenever the line-switch contacts are in the on-hook state;
• (b) applying the rectified signal to input pins of an I-C timer chip whenever the line-switch contacts are on-hook, the chip also having a high-frequency output pin and reset pin for disabling the high-frequency output;
• (c) connecting the high-frequency output to the telephone receiver whenever the line-switch contacts are on hook so that the high-frequency output, when not disabled, operates the receiver as the transducer from the tone ringer;
• and
• (d) connecting the reset pin to circuit ground so as to disable the chip from producing the high-frequency output to the receiver whenever the handset has been lifted from the cradle and the line-switch contacts are thereafter closed, so as to preclude the possibility of a user being rung in the ear.