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Audio Visual Ringer:  extra ring detector with LED and sound output. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 5/02)

Cellular Phone calling Detector:  Flashes a LED when detecting an incoming call.  Powered by one 1.5V cell  (added 4/05)

Chip recorder customizes phone ringer:  07/25/02 EDN Design Ideas  /  (added 1/05)  Companies usually purchase one type of telephone for all employees, which is understandable, especially if they obtain a discount for buying in quantity. One ringer sound for everyone can pose a problem, though, if the sound of a ringing phone makes a dozen people pause and look at their telephones. Equally annoying is the absence of a visual message indicator....

Telephone Ring Generator using 60Hz Power Transformer:  (circuit / design added 8/03)

Telephone Ring Generator  :  (circuit / schematic added 2/03)

Telephone Ring Tone Generator:  (electronic Circuit / Schematic added 10/04)

Telephone Ringer :  The circuit requires four astable multivibrators for its working. Therefore two556 ICs are used here. The IC556 contains two Timers (similar to555 ICs) in a single package. One can also assemble this circuit using four separate555 ICs. The first multivibrator produces a rectangular waveform with1-second ‘low’ duration and2-second ‘high’ duration. This waveform is used to control the next multivibrator that produces another rectangular waveform. (added 3/03)

Telephone Ringer using 555 dual timers #2:  Using modulated rectangular waves of different time periods, The circuit presented here produces ringing tones similar to those produced by a telephone. The circuit requires four astable multivibrators for its working. Therefore two 556 ICs are used here. The IC 556 contains two timers (similar to 555 ICs) in a single package. One can also assemble this circuit using four separate 555 ICs. The first multivibrator produces a rectangular waveform with 1-second ‘low’ duration and 2-second ‘high’ duration. This waveform is used to control the next multivibrator that produces another rectangular waveform. A resistor R7 is used at the collector of transistor T2 to prevent capacitor C3 from fully discharging when transistor T2 is conducting. Preset VR1 must be set at such a value that the two ringing tones are heard in one second. The remaining two multivibrators are used to produce ringing tones corresponding to the ringing pulses produced by the preceding multivibrator stages....   (added 10/05)

Telephone Ringer using Timer ICs:  (electronic Circuit / Schematic added 10/04)

Telephone Ringing Circuits:  how to detect ringing and how to make phones ring (added 5/02)

Telephone Ring-Tone Generation:  DN134 -  Design Notes (Linear Technology) (app note added 2/06)