The GL6851 tone ringer is a monolithic device, which incorporates two oscillators, an output amplifier and a power supply control circuit. The oscillator frequencies can be adjusted over a wide range by selection of external components. One oscillator, normally operated at a low frequency, causes the second oscillator to alternate between its nominal frequency, and a related higher frequency. The resulting output is a distinct warbling tone. The output amplifier will drive either a transformer coupled loudspeaker or a piezo-ceramic transducer. The device can be powered from a telephone line or a fixed d.c. supply. The GL6851 has provision for adjustment of the supply initiation current.