Telephone Tone Ringer Chip Circuit

The  34017A Tone Ringer derives its power supply by rectifying the AC ringing signal. It uses this power to activate a tone generator and drive a piezo-ceramic transducer. The tone generation circuitry includes a relaxation oscillator andfrequency dividers which produce high and low frequency tones as well as the tone warble frequency.TheMC34012  tone-ringer chip derives its power by rectifying the ac ringing signal. That signal is normally at 20 Hz and measures between 70 and 130 volts rms. It uses that power for the tone generator and to drive the piezoelectric transducer. The sound that is produced is a warble that varies between two frequencies, f0/4 (f0 - 4) f0/5. The clock, or fundamental, frequency, f0, is generated by a relaxation oscillator. That oscillator has R2 and C2 as its frequency setting components providing a selectable range of 1 kHz to 10 kHz. Selecting different values for R2 and/or C2 changes the clock frequency, which in turn varies the warble frequencies.For example: with a 4.40 kHz oscillator frequency, the MC34012-1 produces 800 Hz and 1000 Hz tones with a 12.5 Hz warble rate. The MC34012-2 generates 1600 Hz and 2000 Hz tones with a similar 12.5 Hz warble frequency from an 8.0 kHz oscillator frequency. MC34012-3 will produce 400 Hz and 500 Hz tones with a 12.5 warble rate from a 2.0 kHz oscillator frequency. The MC34012 chip comes in three different warble rates at which the warble frequencies (f0/4, f0/5) are varied. These warble rates are fo/320, fo/640, or fo/160 and the different chips are designated as MC34012-1, -2, and -3, respectively.The tone ringer output terminals through which the sound element is driven.The oscillator terminal for the external resistor and capacitor which control the tone ringer frequencies.