The IS200TICIH2A is a high-performance contact input terminal board within the distributed I/O family of the General Electric (GE) Mark VIe control system. As a specific model in the Contact Input with Point Isolation (TICI) series, the IS200TICIH2A provides 24 fully isolated voltage detection channels, specifically designed for acquiring signals from relay auxiliary contacts, switch positions, fuse status, and various discrete signals. This board belongs to the TICIH2 group and is designed for low-voltage control systems with a nominal voltage range of 16 to 32 V DC (typically 24 V DC). Each input is electrically isolated from all others and from the active electronics on the board, ensuring signal acquisition integrity and system noise immunity in the harshest industrial electromagnetic environments.
The core value of the IS200TICIH2A lies in its "point isolation" design: unlike traditional common-ground contact inputs, each input is independently isolated and can be connected to discrete signals from different power systems and different reference potentials, eliminating concerns about ground loops or common-mode interference. Furthermore, the board provides no contact excitation (wetting voltage) on the terminal board itself; all 24 V DC excitation must be supplied externally. This allows the IS200TICIH2A to adapt to various contact loops with different voltage levels while avoiding the impact of an onboard power supply failure on the input channels.
System Positioning and Compatibility
Within the Mark VIe control architecture, the IS200TICIH2A serves as the front-end of the process I/O subsystem, working in close coordination with the PDIA (Digital Input I/O pack). In a simplex control system, one IS200TICIH2A connects to one PDIA I/O pack via the JR1 connector. In a Triple Modular Redundant (TMR) system, the same terminal board connects to the PDIA I/O packs of the R, S, and T sections via the JR1, JS1, and JT1 connectors respectively, enabling 2-out-of-3 voting for the 24 inputs. Each PDIA I/O pack communicates with the controller via dual RJ-45 Ethernet ports, completing the full digital chain from field contact status to controller logic variables.
The IS200TICIH2A is strictly intended for contact inputs with a nominal 24 V DC voltage. For applications requiring 125 V DC or 115/230 V AC voltage levels, the TICIH1 series (such as the IS200TICIH1A) should be selected. The board has no jumpers or hardware settings; all parameters, such as filter times and channel enable, are configured through the PDIA I/O pack using the ToolboxST application software.
Core Functional Features
1. 24 Fully Point-Isolated Inputs
The IS200TICIH2A provides 24 independent contact input channels. Each input is designed with independent isolation spacing on the printed circuit board, ensuring that an overvoltage or ground fault on one channel does not affect other channels. This fully isolated design allows dry or wet contact signals from different power supply sections and voltage levels to be connected to the same terminal board simultaneously, giving system integrators a high degree of flexibility.
2. Voltage Detection Threshold and Range
As a TICIH2 group board, the nominal input voltage for the IS200TICIH2A is 24 V DC, with an allowable operating range of 16 to 32 V DC. An input channel is determined to be in the "contact closed" state when the input voltage exceeds the detection threshold of approximately 9.5 to 15 V DC; below this threshold, it is considered "contact open." This threshold design ensures reliable contact state detection even with some fluctuation in the supply voltage. The board provides hardware input filtering with a nominal time delay of 15 milliseconds: for DC applications, the delay is 15 ± 8 ms; for AC applications (although the TICIH2 is primarily designed for DC, it has some AC adaptability), the delay is 15 ± 13 ms.
3. No Onboard Contact Wetting Current
The IS200TICIH2A board provides no contact excitation power. This means the 24 V DC supply required for all 24 inputs must be provided externally, typically from a DC distribution system within the control cabinet. This design protects the board itself from failures in the wetting current supply. It also allows users to select the optimal wetting current value (via external current-limiting resistors or power supply internal resistance) based on the actual contact type (e.g., gold-plated contacts, high-power contacts) to prevent contact oxidation or erosion.
4. Dual Hardware and Software Filtering
In addition to hardware filtering, the PDIA I/O pack provides configurable software filtering for each input, with selectable delay times of 0, 10, 20, 50, and 100 milliseconds. Software filtering effectively eliminates contact bounce and transient interference, preventing the controller from receiving false state changes. For critical contacts involved in trip protection (such as the 86G lockout or 52G circuit breaker status), a longer filter time (e.g., 50 ms or 100 ms) is typically configured to ensure noise immunity. For general status indication, shorter delays can be chosen for faster response.
5. Pluggable Terminal Blocks and Installation Flexibility
The IS200TICIH2A is equipped with two pluggable Euro-block type terminal blocks, each containing 24 terminals, accepting wires up to #12 AWG (approximately 3.3 mm²). The pluggable design allows cables to be pre-wired to the terminal blocks on the bench, and then the blocks can be inserted as a single unit onto the board. When replacing a board, there is no need to remove wires; simply unplug the blocks, swap the board, and plug the blocks back in. This dramatically reduces downtime. A shield terminal strip connected to chassis ground is located immediately to the left of each terminal block, ensuring proper termination of cable shields.
The board supports DIN-rail mounting (via a metal carrier and plastic insulator) or direct bolt mounting to a panel inside the cabinet, accommodating different control cabinet layouts.
6. Onboard ID Chip and Zero Configuration
A read-only ID chip is integrated onto the IS200TICIH2A board, storing the terminal board's serial number, board type, revision number, and connector location information (JR1/JS1/JT1). The PDIA I/O pack reads this chip during power-up initialization. If a mismatch with the configuration is detected, a hardware incompatibility fault alarm is immediately generated. Additionally, the IS200TICIH2A board has no jumpers, switches, or adjustable components. All configuration is completed via ToolboxST software, enabling true plug-and-play operation.
Diagnostic Functions
The IS200TICIH2A, working in conjunction with the PDIA I/O pack, provides several built-in diagnostic functions:
Excitation Voltage Monitoring: The 24 V DC contact wetting supply voltage is continuously monitored. If the voltage drops below 40% of its nominal value, the PDIA sets and latches a diagnostic alarm, preventing misreading of contacts due to insufficient supply.
Forced Fail-Safe State Test: The PDIA periodically performs a diagnostic test on all input channels associated with this terminal board. During the test, all channels are forced to the "contact open" (fail-safe) state. Any channel that fails to respond correctly is permanently forced to the fail-safe state, and a fault is annunciated. This guarantees that even if a terminal board or connecting cable fails, the system will not falsely interpret a contact as closed.
TMR Voting Consistency Check: In a TMR system, the PDIA I/O packs of the three separate R, S, and T sections independently acquire the same contact signal. If an input from one board does not match the 2-out-of-3 voted value, a fault alarm is generated, indicating a potential problem with the input channel or cabling of that section.
Board ID Mismatch Detection: The ID chip is automatically verified at startup. If the terminal board model does not match the configuration, a hardware incompatibility fault is generated immediately, preventing operational anomalies caused by incorrect board replacement.
Installation and Wiring
To install the IS200TICIH2A, first assemble the plastic insulator and the terminal board onto a metal carrier. Then, snap the carrier onto a standard DIN rail, or secure it directly to a panel using bolts. When wiring, connect the field contact signal wires to the corresponding positions on the terminal blocks. For each input, simply connect the two wires from either side of the contact to the two designated terminals (2 terminals per channel); there is no polarity requirement. Release the pressure screw on the terminal block using a screwdriver, insert the stripped wire end, and tighten the screw to complete the connection.
The 24 V DC wetting current supply for all 24 inputs must be provided by an external power source, typically wired from the DC distribution terminal strip inside the control cabinet to the power terminals of each channel. It is imperative to ensure that the wetting current loop for each channel correctly connects the external contact in series, and that the wetting current magnitude is within the contact's rated value.
Cable shields should be terminated at the shield ground terminal strip located next to the terminal blocks. This strip is internally connected to chassis ground. Correct grounding is critical for ensuring signal integrity in electromagnetically noisy environments.
Application Scenarios
Thanks to its 24 fully isolated channels and suitability for low-voltage 24 V DC, the IS200TICIH2A is widely used for discrete signal acquisition in the following industrial applications:
Circuit breaker auxiliary contact status (e.g., 52G close/open)
Protection relay output contacts (e.g., 86G lockout, 94 trip)
Switchgear door position switches
Selector and transfer switches in control circuits
Field limit switches and proximity switches
Contactor and relay auxiliary contacts
Fuse blown indication contacts
Process interlock and permissive signals
In a TMR system, a single IS200TICIH2A connects simultaneously to three PDIA I/O packs, enabling 2-out-of-3 voted acquisition for 24 critical trip and protection signals. This provides the system with a highly reliable and highly available discrete input solution. In a simplex system, a single terminal board can meet the centralized acquisition needs of 24 general status indication signals.
