Connection apparatus for digital keys telephones and a method in a digital keys telephone system

摘要

In connecting a first digital key telephone 400 to a second digital key telephone 857 in a digital key telephone system, an additional module 855 for implementing data transmission for a call to the first digital key telephone 400 from the second digital key telephone 857 is provided. Synchronizing signal terminals and a B clock terminal of a first unit 801 of the additional module 855 are connected to a second unit 402 of the first digital key telephone 400. Data transmitting and receiving terminals, a D clock terminal and an input/output control port of a microprocessor 404 of the first digital key telephone 400 are connected to the first unit 801. A transformer 807 is connected to the second digital key telephone 857 through a transmission line 821. The transformer 807 is connected to transmission input and output terminals Li, Lo of the first unit 801 through capacitors and diodes 804, 805, 806. IMAGE