US 4,112,427 AGranted

Reversible analog-to-digital converter

AssigneeSiemens Aktiengesellschaft

InventorsErnst Hofer, Peter Hirschmann, Klaus Wintzer

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Abstract

A method and apparatus for a telecommunication installation is disclosed for converting PAM analog signals into PCM digital signals and vice versa. A conversion circuit which is connected to a telephone station comprises an input register for temporarily storing the incoming PCM digital signals and an output register for temporarily storing the outgoing PCM digital signals. This conversion circuit includes a clock pulse generator which enables a counter to count through all its counter positions upon the appearance of each channel time slot pulse of the incoming PCM channel time slot pulse train. The input register and counter are connected to an intermediate register which in turn is connected to a digital-to-analog converter for converting the incoming PCM digital signal into an analog signal. This analog signal is sent to the receiving unit of the telephone station in a first time interval of the counter. The conversion circuit also comprises an analog comparator which is connected to the transmitting unit of the telephone station for receiving PAM analog signals. This PAM analog signal is converted into a digital signal in the intermediate register during a second time interval of the counter. The converted analog signal is then fed to the output register to be sent to the PCM switching center. Thus, the conversion circuit of this invention is time shared for use in converting both digital and analog signals.

Claims16

Dependent claims

A method of converting incoming PAM analog signals into outgoing PCM digital signals, and of converting incoming PCM digital signals into outgoing PAM analog signals in a telecommunication installation having telephone stations, each of said telephone stations comprising a transmitting unit supplying analog signals and a receiving unit accepting analog signals, wherein said telecommunication installation communicates with a PCM switching center by supplying PCM digital signals to said PCM switching center and receiving PCM digital signals from said PCM switching center, said telecommunication installation being in communication with said PCM switching center for the duration of the channel time slot pulses of the PCM channel time slot pulse train, said telecommunication installation comprising an analog-to-digital converter for the conversion of the incoming PAM analog signals into outgoing PCM digital signals, said analog-to-digital converter functioning according to the iterative principle and comprising a counter with a given counting interval, an intermediate register controlled by the outputs of said counter, a digital-to-analog converter following said intermediate register, and an analog comparator with one input connected to the output of said digital-to-analog converter and another input connected to receive analog signals from said transmitting unit which are intended to be converted into digital signals, the output signals of said comparator being supplied to said intermediate register, said telecommunication installation further comprising digital signal converting means including said intermediate register and said digital-to-analog converter for converting incoming PCM digital signals to outgoing PAM analog signals and sending the converted PCM digital signals to said receiving unit of said telephone station, the method comprising the steps of:

sharing the counting interval of said counter by converting the PCM digital signal from said PCM switching center to a PAM analog signal during a first portion of the counting interval of said counter and by converting the PAM analog signal from said transmitting unit of said telephone station to a PCM digital signal during a second portion of the counting interval of said counter;
and,
initiating the counting interval of said counter within which said counter passes through all counter positions upon the appearance of each channel time slot pulse of the PCM channel time slot pulse train from said PCM switching center.

In a telecommunication installation having telephone stations, each of said telephone stations comprising a transmitting unit for supplying PAM analog signals and a receiving unit for receiving PAM analog signals, a conversion circuit connected between said telephone station and a PCM switching center for converting the PAM analog signals supplied by said telephone station into outgoing PCM digital signals and for converting incoming PCM digital signals into PAM analog signals for said telephone station, wherein said conversion circuit communicates with said PCM switching center by supplying PCM digital signals to said PCM switching center and receiving PCM digital signals from said PCM switching center, said conversion circuit being in communication with said PCM switching center for the duration of the channel time slot pulses of the PCM channel time slot pulse train of the incoming PCM digital signal, said conversion circuit comprising:

an input register for receiving and temporarily storing PCM digital signals from said PCM switching center;
a multistage counter with a given counting interval;
a clock pulse generator connected to said counter for enabling said counter to pass through all its counter positions in response to the appearance of each channel time slot pulse of the PCM channel time slot pulse train received by said input register from said PCM switching center;
intermediate register means;
a first logic circuit connected to the outputs of said input register and actuated by said counter for coupling the incoming PCM digital signal from said input register to said intermediate register means in accordance with a first portion of the given counting interval of said counter;
a digital-to-analog converter connected to said intermediate register means for converting the PCM digital signal in said intermediate register means to an analog signal within the first portion of the given counting interval and supplying the analog signal to said receiving unit of said telephone station;
an analog comparator with one input connected to receive the PAM analog signal from said transmitting unit of said telephone station and a second input connected to the output of said digital-to-analog converter;
a second logic circuit connected to the output of said analog comparator and actuated by said counter for coupling the PAM analog signal from said transmitting unit of said telephone station to said intermediate register means and said digital-to-analog converter to convert the PAM analog signal to an outgoing PCM digital signal in accordance with a second portion of the given counting interval of said counter by the combined operation of said analog comparator, said second logic circuit, said counter, said intermediate register and said digital-to-analog converter;
and
an output register connected to the outputs of said intermediate register means for coupling the outgoing PCM digital signal to said PCM switching center.

7 more elements

Dependencies are inferred from the claim text.