The GE IS400TDBTH6AEF is a discrete input/output terminal board designed for the Speedtronic Mark VIe control platform. As a simplex (non-redundant) assembly, it serves as the physical interface between field wiring and the Mark VIe I/O architecture, handling contact inputs and relay outputs for gas turbine, steam turbine, and balance-of-plant control applications where full TMR redundancy is not required.
Product Overview
In the Mark VIe distributed I/O architecture, control logic resides in the controller, while terminal boards like the IS400TDBTH6AEF provide the physical connection point for field signals. This board receives discrete status signals from switches, limit sensors, and interlock contacts, then passes them to compatible PDIO I/O packs for processing. Conversely, it transmits controller commands to field devices through onboard relay outputs.
Key Specifications
Parameter Value
Series Mark VIe
Board Type Discrete I/O Terminal Board
Architecture Simplex (non-redundant)
Contact Inputs 24 group-isolated channels
Input Wetting Voltage 24 / 48 / 125 VDC (field-selectable)
Input Filter 4 ms hardware filter
Relay Outputs 12 Form-C (SPDT) channels
I/O Pack Interface D-sub connectors to PDIO packs
Communication via IONet to Mark VIe controller
Mounting DIN-rail or flat cabinet mount
Operating Temperature 0°C to +60°C (control cabinet environment)
Functional Capabilities
Field Input Acquisition. The board accepts 24 group-isolated contact inputs suitable for limit switches, pressure and temperature switches, start/stop pushbuttons, and safety interlock contacts. Group isolation prevents ground-loop interference between field circuits and cabinet electronics. A 4 ms hardware filter suppresses electrical noise and contact bounce that could otherwise trigger false interlock responses.
Relay Output Control. Twelve Form-C relay outputs provide dry-contact switching for solenoid valves, contactors, indicator lamps, and trip circuits. Each relay is rated for the switching loads typical of turbine auxiliary systems. The relay outputs are electrically separated from the input circuits, maintaining signal integrity across the board.
System Integration. The board connects to compatible PDIO I/O packs through D-sub connectors. Signal data travels from the packs to the Mark VIe controller over the IONet industrial Ethernet backbone. Configuration and diagnostics are performed through GE’s ToolboxST software, which provides channel-level status monitoring and fault reporting.
Application Context
The IS400TDBTH6AEF is intended for Mark VIe installations where simplex I/O is appropriate—typically auxiliary systems, balance-of-plant interfaces, and non-critical monitoring loops. For critical protection circuits requiring triple modular redundancy, the TMR-compatible TDBT variants should be specified instead.
This board is widely deployed in:
Gas turbine auxiliary control cabinets
Steam turbine interlock and monitoring circuits
Combined-cycle plant balance-of-plant systems
Legacy Mark VIe installations requiring simplex spare-part replacement
Compatibility Notes
The IS400TDBTH6AEF is a legacy Mark VIe hardware assembly. Before ordering as a replacement, verify the complete system part number, existing I/O pack type, and field wiring configuration against the original system documentation. The base board model is IS400TDBTH6A; the EF suffix identifies the specific simplex assembly configuration. Different suffix revisions may carry distinct terminal definitions or firmware compatibility requirements and should not be assumed interchangeable without verification.
