Patent ID: 6978000
Filing Date: 2005-12-20
Classification: H04M

Abstract:
1. An interface unit capable of being connected to a main unit of a key telephone system, the main unit connecting a telephone terminal to a telephone network, the interface unit adapted to communicate with the telephone terminal at a high or low transmission speed, the interface unit comprising: a first transmitter configured to transmit a type query signal to the telephone terminal at the low speed; a first receiver configured to receive a type signal from the telephone terminal at the low speed; a second transmitter configured to transmit a speed change request to the telephone terminal at the low speed and change a transmission speed from the low speed to the high speed if the received type signal indicates that the telephone terminal is capable of transmitting data at the high speed; a detector configured to determine whether data is transmitted from the telephone terminal at the high speed or the low speed; and a speed change unit configured to change a transmission speed from the high speed to the low speed when the detector determines that the data is transmitted from the telephone terminal at the low speed.