Digital telephone set capable of being simultaneously used by a plurality of persons by using one transmission line

A digital telephone set connected to a digital data exchange through a transmission line, said digital data exchange being able to transmit/receive, through said transmission line, a time division multiplexed signal into which a plurality of digital speech signals are multiplexed in a time division fashion, said digital telephone set comprising:

• a telephone body;
• a plurality of handsets mounted on said telephone body for converting input sounds into input analog speech signals and for converting output analog speech signals into output sounds;
• a plurality of analog-to-digital converters connected to said handsets for converting said input analog speech signals into input digital speech signals;
• a plurality of digital-to-analog converters connected to said handsets for converting output digital speech signals into said output analog speech signals;
• a set of dialling keys mounted on said telephone body for producing a numerical signal;
• a control device connected to said dialling keys for producing input control data in response to said numerical signal and for producing an output control signal in response to output control data;
• and
• a multiplexing/demultiplexing circuit connected to said transmission line, said control device, said analog-to-digital converters, and said digital-to-analog converters for transmitting/receiving transmission/reception time division multiplexed signals to/from said digital data exchange through said transmission line, said multiplexing/demultiplexing circuit being for multiplexing said input digital speech signals and said input control data into said transmission time division multiplexed signal and for demultiplexing said reception time division multiplexed signal into said output digital speech signals and said output control data.