IBM 2790

The IBM 2790 Data Communications System is a family of devices intended for "in-plant data communications and production monitoring." It is described as a two-way data communications system designed to accommodate large volumes of short messages from many in-plant locations or from smaller groups of terminals at remote locations.

The 2790 consists of the following components, all connected by a two-wire loop operating at 500 kbit/s. The 2715 can support up to 32 KB of magnetic core memory with a 1.2 μs cycle time, an internal disk for microcode load, a 2740 printer/keyboard, and a real time clock.

Firstly it consists of one IBM 2715 Transmission Control Unit, which controls the other system components. The 2715 provides terminal control, transaction assembly, data-entry checking, message routing, transaction storage, and transfer of data to and from a System/370, IBM 1800 Data Acquisition and Control System or an IBM System/7. There are numerous data entry devices that can be attached:
 * 2715 Model 1: Used for local operation
 * 2715 Model 2: Used for remote attachment with a binary synchronous communication adapter such as a 270x communications controller.
 * The IBM 2791 Area Station is a tabletop unit attached to the 2790 loop. The 2791 can read ten column identification badges and eighty column punched cards, and has a twelve key pad for direct entry of numeric data.  The 2791 can attach up to thirty-two 2795/2796 data entry units, a 1053 printer, up to three 1035 remote badge readers, and an OEM device.  The 2791 has nine user defined "transaction buttons".  Up to 100 2791/2793 can be attached.
 * The IBM 2793 Area Station is similar, but lacks the ability to accept input data directly. It can attach up to thirty-two data entry units and a 1053 printer. Up to 100 2791/2793 can be attached.
 * The IBM 2795, 2796 and 2797 Data Entry Units are compact industrial units for reporting job and machine status and production information.  Both have two ten-position switches and a ten column badge reader.  The 2796 has an additional two switches and allows for manual entry of up to four digits.
 * 2740 Communications Terminal (one)
 * 2798 Guided Display Units. This is a versatile and compact data entry and output unit with a 56 character keyboard, 8 control keys and 16 position visual display.  Up to 12 can be attached.