The IC LS1240A from SGS Thompson is specifically designed for generating a 2 tone ringtone generator circuit. Thus the IC specifically becomes suitable for landline telephones for producing the ringtones when a call is received.

However with little modifications the IC can be easily utilized for normal applications, in circuits where a double tone alarm may be required.

Technical Specifications

Basically the IC is a 8-pin DIL chip resembling the IC 555 and has the following specs:

  • Very low current consumption yet good audible response at the output.

  • Internal built-in rectifier stage for rectifying an AC input supply, a filter capacitor is also a built-in feature of the IC.

  • Hardly any external components required for setting up the circuit.

  • The tone of the output musical audio can be adjusted externally through a resistor.

  • If the IC os used inside a landline telephone then the supply to the IC is derived from the line voltage via a 1uF capacitor.

  • The IC is able to drive a piezo electric transducer directly without the need of inductors or amplifiers.

  • The IC is also capable of driving a small loudspeaker directly for generating the musical output.

  • However the speaker must be rated at minimum of 50 Ohms.

  • The following 2 tone ringtone generator circuit shows how to configure the IC LS1240 as a two tone musical signal generator circuit.

Pinout Details of the IC LS1240 dual tone generator IC

Pinout S[ecs of the IC LS1240 dual tone generator IC

Circuit Diagram of two tone music generator using IC LS1240

Two Tone Generator using piezo element


Need Help? Please send your queries through Comments for quick replies!