through the speech packet processor part 33 or the telephone interface control part 34 therefore when a speech signal arrives while the packet communication unit 30 is making communication that signal is dealt with as in the case of usual busy mode processing by the exclusive control function more concretely when the packet communication unit 30 starts to make communication with the telephone 21 connected to the private branch exchange network 13 the processor part 31 changes over the switch part 36 to supply the speech input to the telephone interface control part 34 and cuts off the supply of the speech input from the speech packet processor part 33 when another speech signal arrives from the other packet communication unit 14 under the above situation the processor part 31 generates a packet indicating that the packet communication unit 30 is now busy and this packet is transmitted from the speech packet processor part 33 to the signal transmitting packet communication unit 14 through the lan 101 on the other hand when the packet communication unit 30 starts to make communication with the other packet communication unit 14 connected to the lan 101 the processor part 31 changes over the switch part 36 to supply the speech input to the.