Ring signal generator for generating ring signals of different frequencies and power levels in response to user selection

Claim 1

A ring signal generator for generating any one of a plurality of types of ring signals of different frequencies and power levels in response to an input selection by a user, comprising: a source of a user control signal for selecting any one of the plurality of ring signals; a controlled clock signal generator responsive to said user control signal and including a master oscillator, first means for producing a first clock signal having a frequency corresponding to that of the ring signal type selected via said user control signal, and second means for producing a second clock signal having a frequency which is a fixed submultiple of the frequency of said first clock signal; sine-wave converter means including a switched capacitor low pass filter (LPF) for receiving said first and second clock signals as inputs and operating to pass a sine-wave component of said second clock signal at said selected ring signal frequency while blocking higher order harmonics thereof and to output an analog sine wave at said selected ring signal frequency; and a power amplifier coupled to the output of said sine-wave converter means for amplifying said analog sine wave to a voltage output level corresponding to that of the ring signal type selected via said user control signal.