Northern Telecom Limited

Marc E Bonneville

Terence N Thomas

Douglas C Wadsworth

In a loudspeaker telephone, improved power transfer is achieved by connecting the drive circuit for the loudspeaker in parallel with the input and output of the usual series regulator, the output of the regulator and one of the power supply connections of the drive circuit being connected, in common, to supply other circuitry in the telephone set. This other circuitry might comprise a microprocessor and other signal processing circuitry. Such a configuration means that the current passing through the speaker drive circuit also passes through the other circuitry. In effect, it is 're-used' instead of being added, as would be the case if the drive circuit were connected in parallel with the other circuitry. In the case of a positive series regulator, the series regulator supplies current when the current requirement of the other circuitry exceeds that received from the drive circuit. When the current from the drive circuit exceeds that required by the other circuitry, the series regulator is arranged to sink the excess current. A suitable push-pull regulator may comprise a power operational amplifier.

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Nepean, Canada

Marc E Bonneville