Description
The three-tone ringing integrated circuit U4076B, in conjunction with a piezo transducer or loudspeaker replaces the normal electromechanical telephone bell. It is operated with the ringing current from the exchange. There is also a possibility of operating the IC with the dc supply voltage, being developed for large operating range. The integrated circuit is overload protected.

Features
● Three-tone ringing sequence with 800 Hz, 1067 Hz and 1333 Hz
● Sequence frequency adjustable between 2.5 Hz and 25 Hz
● Adjustable volume
● Push-pull output stage
● Piezo transducer or loudspeaker connection
● Common input for frequency and call recognition
● Reduced pulse duration for electromagnetic transducers
● Clock oscillator with ceramic resonator or LC series cct possible
● Input protective diode
● On-chip rectifier bridge
● Protection circuit against ringing in a parallel circuit

Benefit
● Suitable for German Post Office Specification, FTZ 121671 Pfl. 3, edition dated 24.03.82