PURPOSE: To display temperature and humidity information received from other terminal on a display device on an own terminal by providing a temperature and humidity sensor and the display device at a terminal.

CONSTITUTION: When a channel is established between terminal devices 1a and 1b via a talking line 11 and an exchange 10, a controller 4 in the terminal actuates a channel switch 9a for a prescribed period via a control line 13 to digitize an identification pattern in 8 bits representing temperature data or humidity data and an output of the temperature and humidity sensor 7 by an A/D converter 2. This information is transmitted to the terminal device of the opposite party via a branching circuit 12 without interferring the transmission and reception of the information via a handset 3 and the A/D converter 2 and displayed on the own display device 8 when required. The terminal device 1b of the opposite party receives this temperature and humidity data on a display driving operator 6 to identify whether the data is the temperature or the humidity data and displays the data on the display device 8.