The SL2418 is a monolithic integrated circuit telephone tone ringer with bridge diode, when coupled with an appropriate transducer, it replaces the electro-mechanical bell. The 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 frequency (fR) alternating with a low frequency (fL) 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.

• On chip high voltage full wave diode bridge rectifier
• Low current consumption, in order to allow the parallel operation of the 4 devices
• Low external component count
• Tone and switching frequencies adjustable by external components
• High noise immunity due to built-in voltage-current hysteresis
• Activation voltage adjustable
• Internal zener diodes to protect against over voltages
• Ringer impedance adjustable with external components