270x is a generic name for a family of IBM non-programmable communications controllers used with System/360 and System/370 computers.

It had two multiplexor channel interfaces for connection to one or two host computers.

The 2703 supported up to 176 half-duplex start-stop or Binary Synchronous communication lines.

The 2703 attached to a single multiplexer channel; each communication line occupied a subchannel.

It had a four or eight byte buffer per line to reduce data transfer to and from the host computer.