Receiving section of a telephone

#The present invention relates to the field of transceivers, and, more particularly, to a receiver section of a telephone.

#A signal received by a telephone from a digital telephone network is demodulated, processed in digital form, converted to analog form, and is amplified before being applied to an electroacoustic transducer. The receiver section of a telephone can be represented schematically as shown in FIG. 1.

#A demodulated digital signal RX-IN produced by a receiving and demodulating unit 10 is applied to the input of a processing unit 11. The processing unit 11 converts the demodulated digital signal to analog form, filters and amplifies the analog signal. The analog signal leaving the processing unit 11 is applied to the input of a power amplifier 12 for transferring the signal to an electroacoustic transducer 13, such as an electromagnetic earphone or speaker, with sufficient electrical power for its operation.

#The invention will be more clearly understood from the following detailed description of various embodiments, provided by way of examples, and therefore, without any restrictions, with reference to the attached drawings, in which:

#FIG. 1 is a block diagram of a receiver section of a telephone according to the prior art; and

#FIGS. 2-4 are block diagrams respectively illustrating an embodiment according to the present invention.

#In FIG. 2, elements identical or corresponding to those of FIG. 1 are indicated by the same reference numbers. A processing unit 11 with a balanced structure receives at its input a demodulated digital signal RX-IN, and supplies a balanced analog signal at two outputs. The outputs of the processing unit 11 are coupled to the inputs of a differential amplifier 12. More particularly, each output is connected to one of the inputs of the amplifier through a respective resistor R1A, R1B in series with an n-channel MOS transistor M1A, M1B operating as an electrical switch.

#Each of the differential outputs 15, 16 of the amplifier 12 is connected, respectively, to the inverting and non-inverting inputs of the amplifier through a resistor R2A, R2B in series with a MOS transistor M2A, M2B. Each MOS transistor M2A, M2B is biased for conduction. An electroacoustic transducer 13, i.e., a speaker, is connected between the outputs 15, 16 of the differential amplifier 12.

#The processing unit 11 and the differential amplifier 12 are supplied power from a voltage source. The processing unit 11 and the differential amplifier 12 each have circuit means which enables or disables the power supply according to a signal applied to respective enabling terminals 17, 18.