INTRODUCTION
The KA2418B/28 is a monolithic integrated circuit telephone tone ringer with bridge diode, when coupled with an appropriate transducer, it replaces the electromechanical bell. This device is designed for use with either a piezo transducer or an inexpensive transformer coupled speaker to produce a pleasing tone composed of a high frequencys (fH1, fH2) alternating with a low frequency (fS) resulting in a warble frequency. The supply voltage is obtained from the AC ring signal and the circuit is designed so that noise on the line or variation of the ringing signal can not affect correct operation of the device.

FEATURES
· Built-in full wave bridge diode rectifier
· Low current consumption, in order to allow the parallel operation of the 4 devices
· Few external components
· Tone and adjustable switching frequencies by external components
· High noise immunity due to built-in voltage to current hysteresis
· Adjustable activation voltage
· Internal zener diodes to protect against over voltages
· Adjustable ringer impedance with external components.

APPLICATIONS
· Electronic telephone ringers
· Extension ringers