The IS200ISBBG1A is an ISBus Bypass Board designed by General Electric (GE) for its control systems. This board is the standard version within the ISBB series, primarily used for connection between an ISBus full duplex source (either a BAIA or an ACL module) and the ISBus. It provides the capability to bypass a node of the ISBus when either power to the node is interrupted or an interlock connection within the full duplex interface is opened.
The IS200ISBBG1A board plays a critical role in bypass protection for ISBus communication within GE control systems. Through its bypass relay, it achieves flexible signal routing: when the board is powered normally and the interlock is closed, it connects the transmit signals from the full duplex input (P1) to the transmit output (P2), and simultaneously connects the signal from the receive input (P3) to the full duplex output (P1). When the board is de-energized, it automatically bypasses the signal from the receive input (P3) directly to the transmit output (P2), implementing node bypass functionality and ensuring uninterrupted communication on the ISBus.
Key features of the IS200ISBBG1A include:
Node Bypass Function: Automatically bypasses a node when power is lost or the interlock is opened, ensuring uninterrupted ISBus communication.
Electrical Isolation: Signal isolation greater than 1 MΩ @ 500 V rms ensures system safety.
Status Indication: 2 LED indicators provide visual status for transmit data input and bypass relay power.
Flexible Power Options: 24 V dc power can be provided via P1 or TB2.
Configurable Interlock: Jumper JP1 allows selection of whether to bypass the external interlock signal.
Passive Signal Conditioning: Signals are only interrupted and rerouted via the relay; no active conditioning circuits.
Compact Design: Compact packaging achieved through connectors and a terminal block.
The board features three plug connectors (P1, P2, P3), one terminal block (TB2), and one configuration jumper (JP1). The board has a simple and reliable design suitable for industrial control environments.
II. Main Functions
The primary functions of the IS200ISBBG1A include, but are not limited to, the following:
1. Node Bypass Protection
The core function of the IS200ISBBG1A board is to provide node bypass protection via a bypass relay. If 24 V dc is not supplied to the ISBB board, the board automatically enters bypass mode:
The transmit connection between P1 and P2 is interrupted (broken).
The receive connection between P3 and P1 is interrupted (broken).
The receive input from P3 is directly connected to the transmit output on P2: RECV DATA IN+ connects to XMIT DATA OUT+, and RECV DATA IN- connects to XMIT DATA OUT-.
This design ensures that even if a node loses power, the ISBus communication link remains uninterrupted, enhancing system reliability.
2. Normal Mode Signal Routing
When the board is powered normally (24 V dc available) and the interlock connection on P1 is closed, the bypass relay is energized, providing the following signal routing:
Transmit input from P1 (XMIT DATA IN+/-) is connected to the transmit output on P2 (XMIT DATA OUT+/-).
Receive input from P3 (RECV DATA IN+/-) is connected to the receive output on P1 (RECV DATA OUT+/-).
3. Bypass Relay Characteristics
The bypass relay features the following characteristics:
Pick-up Voltage: > 14.5 V
Dropout Voltage (Brown-out Condition): 11.0 ± 1.0 V dc (when the 24 V input slowly decreases to zero).
Dropout Voltage (Normal Operation): < 10 V (when the relay interlock input voltage slowly decreases to zero while the voltage at P1-7,8 remains at 24 V dc).
Rated Input Voltage: Nominal 24 V dc, maximum 30 V dc.
Contact Current Rating: > 200 mA @ 10 V rms.
Isolation: At least 40 dB at 1 MHz.
Maximum Operating Power: < 1 W (for one or multiple relays).
4. Power Options
The board can receive 24 V dc power via two methods:
P1 Connector: Via pins 7 (positive) and 8 (return).
TB2 Terminal Block: Via pins 1 (positive) and 2 (negative), serving as an auxiliary or external power source.
Neither side of the input voltage is referenced to any other voltage or return on the board.
5. Signal Isolation
Input signal isolation is greater than 1 MΩ at 500 V rms for 1 second, ensuring electrical isolation and system safety.
6. LED Status Indication
The board features two LED indicators:
7. Configurable Interlock
Jumper JP1 selects the interlock operating mode:
Position 1-2 (Default): The board must have the external interlock closed to energize the relay(s).
Position 2-3: Shorts out the interlock. Power must still be applied to the board via P1-7,8 or TB2-1,2 to energize the relay(s).
III. System Applications
1. Application in ISBus Communication Systems
The IS200ISBBG1A is a key board for ISBus communication bypass protection within GE control systems. Its roles within the system include:
Node Bypass: Automatically bypasses a node upon power loss or interlock opening, ensuring uninterrupted bus communication.
Communication Relay: In normal mode, transmits signals from the full duplex source to the ISBus and returns signals from the ISBus to the full duplex source.
2. Coordination with BAIA and ACL
The IS200ISBBG1A can be connected between an ISBus full duplex source (BAIA or ACL module) and the ISBus. Through its flexible power and interlock options, it can adapt to different system configuration requirements.
3. Typical Application Scenarios
High-Reliability Control Systems: In applications demanding high availability, the node bypass function prevents single points of failure from causing communication interruptions.
Redundant Communication Networks: Provides node bypass protection in redundant ISBus networks.
Remote I/O Systems: Applied in remote I/O nodes to ensure a single node failure does not affect the entire communication network.
Industrial Process Control: Ensures communication reliability in distributed control systems.
IV. Detailed Interface Description
1. P1 Full Duplex Connector
P1 is an 8-pin RJ45 type connector for connecting a full duplex source (BAIA or ACL). Pin assignments are as follows:
| Pin | Nomenclature | Description |
| 1 | XMIT DATA IN+ | Positive RS-422 input |
| 2 | XMIT DATA IN- | Negative RS-422 input |
| 3 | RECV DATA OUT+ | Positive RS-422 output |
| 4 | RELAY INTERLOCK | Routing of 24 V dc to the full duplex source |
| 5 | RELAY INTERLOCK RTN | Routing of 24 V dc back from the full duplex source to energize the relay(s) |
| 6 | RECV DATA OUT- | Negative RS-422 output |
| 7 | INTERLOCK 24VDC | 24 V dc input |
| 8 | INTERLOCK 24VDC RTN | 24 V dc return |
2. P2 Transmit Data Connector
P2 is an 8-pin RJ45 type connector for connecting to the ISBus transmit lines. Only pins 3 and 6 are used:
| Pin | Nomenclature | Description |
| 1,2 | NC | Not Connected |
| 3 | XMIT DATA OUT+ | Transmitter positive output to ISBus (+) |
| 4,5 | NC | Not Connected |
| 6 | XMIT DATA OUT- | Transmitter negative output to ISBus (-) |
| 7,8 | NC | Not Connected |
3. P3 Receive Data Connector
P3 is an 8-pin RJ45 type connector for connecting to the ISBus receive lines. Only pins 3 and 6 are used:
| Pin | Nomenclature | Description |
| 1,2 | NC | Not Connected |
| 3 | RECV DATA IN+ | Receiver positive input from ISBus (+) |
| 4,5 | NC | Not Connected |
| 6 | RECV DATA IN- | Receiver negative input from ISBus (-) |
| 7,8 | NC | Not Connected |
4. TB2 Auxiliary Interlock Power Terminal Block
TB2 is a 2-pin terminal block for connecting an auxiliary/external power source:
| Pin | Nomenclature | Description |
| 1 | AUX INTERLOCK 24VDC | 24 V dc from an auxiliary or external power source |
| 2 | AUX INTERLOCK 24VDC RTN | 24 V dc return |
V. LED Indicators and Jumper Configuration
1. LED Indicators
The board features two LED indicators providing status information:
| LED | Description |
| LED1 | Transmit Data Input Indication, lights when data input is present |
| LED2 | Bypass Relay Power Indication, lights when relay is energized |
2. Jumper JP1 Configuration
| Position | Description |
| 1-2 | Default position; board must have the external interlock closed to energize the relay(s) |
| 2-3 | Shorts out the interlock; power must be supplied to the board via P1-7,8 or TB2-1,2 to energize the relay(s) |
VI. Installation and Maintenance
1. Mounting Location
The IS200ISBBG1A board is typically mounted inside a control cabinet and connects to the system via connectors. It can be mounted on a DIN rail or directly fixed to a panel.
2. Installation Steps
Connect P1: Connect the full duplex source (BAIA or ACL) to the P1 connector.
Connect P2 and P3: Connect the ISBus transmit and receive lines to the P2 and P3 connectors, respectively.
Connect Power: Select either P1-7,8 or TB2 for power supply as required.
Configure Jumper: Set JP1 according to system requirements.
Check LEDs: After power-up, verify that the LEDs indicate normal status.
3. Maintenance Recommendations
Periodic Inspection: Check connectors for secure connection and wires for looseness.
Cleaning: Regularly clean the board to prevent dust accumulation.
ESD Protection: Wear a grounding strap when handling the board and store it in anti-static bags.
Spare Parts Management: Maintain a spare ISBBG1A board to reduce downtime in case of failure.
