Abstract: A coupling device provides for an inexpensive coupling between two data processing systems at a relatively low expense, even when a large number of channels is involved. The coupling device provides, for each data processing system, a clock pulse line, a transmitting bus, a receiving bus and an address bus. For each address, two memory cells are provided and have associated address decoders. The address decoders receive the addresses by way of the address buses and with identification of an associated address, transmit decoding signals to the memory cells. A pair of clock pulse controls provide sequences of write commands and read commands for controlling the writing of individual bits of the two transmitting buses into the addressed memory cells and cause transfer of these bits to the receiving buses.