BL1240
ELECTRONIC TWO – TONE RINGER
Features
Low current consumption, in order to allow the parallel operation of 4 devices.
Integrated rectifier bridge with zener diodes to protect against overvoltages.
Little external circuitry.
Tone and switching frequencies adjustable by external components.
Integrated voltage and current hysteresis.
Description
BL1240 is a monolithic integrated circuit designed to repace mechanical bell in
telephone sets in connection with an electro-acoustical converter. It can drive directly
a piezoceramic converter (buzzer) or a dynamic loudspeaker.
The output current capability of BL1240 is higher than standard ringer. For driving a
dynamic loud-speaker BL1240 can simply use a decoupling capacitor, thus
eliminating the usual transformer.
No current limitation is provided on the output stage of BL1240, so a minimum load
DC of 50 ohm is adviced, in series with a proper capacitor.
The two tone frequencies generated are switched by an internal oscillator in a fast
sequence and made audible across an output amplifier in the loud-speaker, both tone
frequencies and the switching frequency can be externally adjusted.
The supply voltage is obtained from the AC ring signal and the circuit is designed so
that noise on the line or variatins of the ringing signal cannot affect correct operation
of the device.
http://www.belling.com.cn
-1-
8/14/2006
Wrote by 2006
Total
5 Pages
BELLING [ SHANGHAI BELLING CO., LTD. ]
