IBM 2701 Data Adaptor Unit

Mainframes in the 1960s and 1970s such as the IBM 360 were huge complicated systems which filled large rooms. Some even had smaller (in relative terms - still large compared to the average machine now) computers to help them with the amount of information that was needed to be sent into them from a number of sources. These computers were known as Front End Processors or Communication Controllers and they handled data communications allowing the mainframe to concentrate on the jobs at hand [1].

The IBM 270x family, of which the 2701 Data Adaptor Unit was a member of, was an early example of communication controller and worked with the IBM 360 and 370. The 2701 "greatly expands the input/output capabilities of the IBM System/360" [2] by helping to interface to and control information flow from peripherals like the IBM 7701 Magnetic Tape Transmission Unit. The IBM 2701 was introduced in 1964 and replaced by the IBM 3704 in 1972.

Public domain image from SDASM Archives

[1] Barry Wilkinson & David Horrocks, Computer Peripherals (Edward Arnold, 1987) p. 281
[2] IBM 2701 Data Adaptor Unit Principles of Operation (IBM, 1965) p. 5