IS220PTURH1B is an I/O pack developed by GE under the Mark VI series. The Mark VI was utilized to regulate the HRSG (boiler) and auxiliary plant controls in order to effectively control and safeguard the gas and steam turbine.
Several I/O-specific cards were built to interface with the balance of plant devices (such as motor-operated valves), and various blocks for controlling the balance of plant operations were developed and written (such as boiler drum level control, etc.). Mark VI and Mark VIe have both been used in combined cycle power plants as DCS and turbine controls.