Description
GL6840A are monolithic integrated circuits designed to replace the mechanical bell in telephone sets, in connection with an electro acoustical converter. The device can drive either directly a piezo ceramic converter(buzzer) or a small loudspeaker. In this case a transformer is needed. The two tone frequen cies generated are switched by an internal oscillator in a fast sequence and made audible across output amplifiers in the transducer, both tone frequencies and switching frequency can be externally adjusted. The supply voltage is obtained from the AC rings signal and the circuit is designed so that noise on the line or variations on the ringing signal cannot affect the correct operation of the devices.
The output bridge configuration allows to use a high impedance transducer with acoustical results much better than in a single ended configuration. The two outputs can also be connected independently to different converters or actuators(acoustical, opto and logic)

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
• Bridge output configuration