SC1240

w w telephone sets in connection with an t e ELECTRONIC TWO-TONE RINGER SC1240 e h S a DESCRIPTION Outline Drawing t a The SC1240 are monolithic integrated circuits D . designed to replace the mechanical bell in w electro-acoustical converter. The devices can drive directly a piezocera mic converter (buzzer). The two tone frequencies generated are switched by an internal oscillator in a fast sequence and made audible across an ou tput a mplifier in the loudspeaker, both tone frequ encies 4U m o .c Silicore and the switching frequency can be externally adjusted. The signal and the circuit is designed so that noise on th e line or variations of the ringing signal cannot affect correct operation of the device. FEATURE z z z z z Low current consumption, in order to allow the parallel op eration of 4 devices. Integrated rectifier bridge with zener diodes to protect ag ainst over voltage. Integrated voltage and current hysteresis Little external circuitry. Tone and switching frequencies ad justab le by external co mponents. BLOCK DIAGRAM Buzzer Line Rectifier Capacitor Null 5 8 7 6 In Threshold Circuit Output Rectifier Stage With Hysteresis Bridge w w w t a .D S a e h U 4 t e .c m o PIN CONNECTION Line Ground 1 2 3 4 8 Line 7 Rectifier Capacitor 6 5 Null Buzzer In Switching Frequency Generator 1 Line Tone Frequency Generator Sweep Rate Control Capacitor Output Frequency Control Resistor 2 4 3 GND Sweep Rate Output Frequency Control Capacitor Control Resi...