Semiconductor circuits for the automatic generation of tone sequences of different tones. A bistable switch having a control input activated by start signal controls a voltage stabilizing circuit which in turn controls an RC-oscillator. Several frequency dividers are driven by the oscillator for producing divider outputs as tone signal outputs furnishing individual tone frequencies corresponding to the tone sequences to be produced. A general cycle control has inputs controlled by the first divider output. Modulator modules driven by the cycle control and by the tone signal outputs, are connected to the digital-to-analog converters which produce tone signal outputs that correspond to the individual tone frequencies. The digital-to-analog converters have outputs that are jointly connected to an electro-acoustic transducer, such as a loudspeaker.
An exponentially decaying chime sound is generated with a single tri-statable output pin from a microprocessor which is implemented using a single digital output pin line to create states of low, high and disconnect which are input to a control circuit for output to a speaker. Preferably, the control circuit comprises a low pass filter in series with a buffer. Preferably, the buffer is a Darlington transistor. Preferably, the speaker is an electro-mechanical device, alternatively it may be a piezo-resistive device. A method is disclosed for generating a desired audible chime signal with a chime generating circuit regulating a tri-statable output via a single pin of a microprocessor to approximately generate a desired signal frequency, and preferably includes regulating said tri-statable output to produce amplitude decay of the desired signal frequency over time.
