IBM 1800 Data Acquisition and Control System

The IBM 1800 Data Acquisition and Control System (DACS) was a process control variant of the IBM 1130 with two extra instructions (CMP and DCM), extra I/O capabilities, 'selector channel like' cycle-stealing capability and three hardware index registers.
IBM announced and introduced the 1800 Data Acquisition and Control System on November 30, 1964, describing it as "a computer that can monitor an assembly line, control a steel-making process or analyze the precise status of a missile during test firing."
Overview.
Unlike the 1130, which was a desk-like unit, the 1800 is packaged in 6 foot high, EIA Standard 19 inch racks, which are somewhat taller than the racks used by S/360 systems of the same vintage, but the internal gates and power supplies were very much the same. Many 1800 cabinets show a distinct "ding" on the vents at the top of the chassis, where movers discovered that the door into a computer room was not quite tall enough for the 1800 cabinet.
The IBM 1500 instructional system was introduced by IBM on March 31, 1966, and was based on an IBM 1130 or IBM 1800 computer. It supported up to 32 student work stations, each with a variety of audiovisual capabilities.
Two 1800s with automatic switchover between them powered each IBM 1750, 2750 and 3750 Switching System.
Components.
The IBM 1800 DACS consisted of:
Use.
The IBM 1800 systems were used mainly in the process industry plants worldwide, such as in the 1971 installation on Blast Furnace No. 5 of Chiba Works of Kawasaki Steel Company, now part of JFE Group.
In June 2010 the last four operating IBM 1800s operating at Pickering Nuclear Generating Station in Pickering, Ontario, Canada were removed from service. Pickering is still using four ES-1800 computers which are IBM 1800 hardware emulators built by Cable & Computer Technologies. A video showing the end of the Pickering IBM 1800 boot sequence is available on YouTube 
Until 1984, Exxon USA (EUSA) had 18 IBM 1800 systems deployed at all 5 of its refineries. They were replaced with Honeywell TDC3000 process control systems.