Portable-to-portable talk system for cordless telephone

A portable-to-portable talk system for cordless telephone where a base unit and portable units are linked via a radio transmitter-receiver, said base unit comprising:

• a first transmitter-receiver having a control channel and a plurality of talk channels;
• a portable-to-portable line setting section for causing said first transmitter-receiver to transmit a channel number of a vacant talk channel selected from said plurality of talk channels to a first portable unit and to a second portable unit over said control channel upon reception of a connection request from said first portable unit over said control channel,
• said portable-to-portable line setting section causing said first transmitter-receiver to switch from said control channel to said vacant talk channel after said channel number of vacant talk channel is transmitted from said first transmitter-receiver over said control channel,
• said portable-to-portable line setting section connecting a receiver output of said first transmitter-receiver to a transmitter input of said first transmitter-receiver after said channel number of vacant talk channel is transmitted to said first and second portable units;
• each of said plurality of portable units comprising:
• a second transmitter-receiver having said control channel and said plurality of talk channels, said second transmitter-receiver transmitting said connection request to said base unit over said control channel when requesting a connection to other portable unit, said second transmitter-receiver being switched from said control channel to said vacant talk channel upon reception of said channel number of vacant talk channel from said base unit over said control channel;
• A Tx/Rx selecting signal generator for generating a signal commanding a switching of said second transmitter-receiver between Tx mode and Rx, said Tx/Rx selecting signal being transmitted over said vacant talk channel to other portable unit via said base unit when an operator of portable unit completes his speech;
• a Tx/Rx selector for causing said second transmitter-receiver to operate as a receiver when said TX/Rx selecting signal is outputted from said TX/Rx selecting signal generator, said Tx/Rx selector causing said second transmitter-receiver to operate as a transmitter upon reception of said TX/Rx selecting signal from other portable unit via said base unit over said talk channel so that an operator is permitted to begin his speech.