ATM/STM COEXISTING NETWORK SYSTEM

PROBLEM TO BE SOLVED: To provide an ATM/STM(asynchronous transfer mode/synchronous transfer 1 N mode) coexisting network system which is very economical with superior operability whereby an ATM system is introduced without changing a pre-existed system. SOLUTION: The ATM/STM coexisting network system where a communication system by an asynchronous transfer mode and the communication system by the synchronous transfer mode are coexisted is constituted in such a way that a first converting means 29 converts the first input signal of the synchronous transfer mode into a cell format where an address for the asynchronous transfer mode is added so as to output it as a first asynchronous transfer mode cell, a second converting means 46 takes-out the asynchronous transfer mode cell from the second input signal obtained by multiplexing the asynchronous transfer mode cell by the syncrhonous transfer mode so as to output it as the second asynchronous transfer mode cell and an output control means 34 controls output destinations(subscriber terminal equipment) in accordance with the address indicated to the first and second asynchronous transfer mode cells so as to output the respective cells to the subscriber terminal equipments.