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SPECIFICATIONS:
Part No: DS3800HNMB
Manufacturer: General Electric
Series: Mark IV
Product Type: Null Modem Communication Card
Operating Voltage: +5V DC
Voltage Levels: ±12V
Frequency Range: Up to 100 kHz
Dimensions: 13.528 x 8.466 x 3.820
Operating Temperature: 0°C to 60°C
Weight: 5 kg
Country of Origin: USA
Availability: In Stock
FUNCTIONAL DESCRIPTION:
DS3800HNMB is a Null Modem Communication Card manufactured and designed by General Electric and is part of the Mark IV Series used in GE Speedtronic gas turbine control systems. The Null Modem Communication Card is designed to enable direct serial communication between two data terminal equipment (DTE) devices, such as computers or controllers, without the need for a modem or intermediary data communication equipment (DCE). It achieves this by internally crossing the transmit (TX) and receive (RX) lines, allowing data sent from one device to be received by the other. This type of communication is ideal for system configurations, diagnostics, and interfacing with legacy or industrial equipment that uses the RS-232 protocol.
INSTALLATION:
The Null Modem Communication Card must be used with proper ESD handling procedures to prevent component damage. Begin by ensuring all power sources to the host system and peripheral devices are fully disconnected. Insert the card into the designated serial communication or expansion slot—typically a VME, ISA, or PCI slot, depending on the system architecture. Secure the card using the mounting screws to avoid vibration-induced disconnection. Once mounted, connect the serial port of the card to the target DTE device using a null-modem RS-232 cable with the appropriate pinout configuration (often DB9 or DB25 connectors). It is essential to verify that the cabling matches the wiring scheme required for null modem communication, especially the crossover of TXD and RXD, and the correct mapping of control signals like RTS/CTS.
OPERATION:
The Null Modem Communication Card enables two-way serial communication by internally reconfiguring the signal paths to support direct device-to-device data exchange without the need for intermediary devices. It transmits digital data via the RS-232 voltage level standard, typically ±12V for logic high/low. Communication parameters—such as baud rate, data bits, parity, stop bits, and flow control—must be configured identically on both devices to establish reliable communication. Depending on the firmware or software support, the card may also provide buffered transmission, FIFO queues, and error detection features such as parity checks. For applications requiring hardware flow control, the card supports full handshake modes (RTS/CTS and DTR/DSR), ensuring reliable data integrity during high-speed transmissions.
COMPATIBILITY:
The Null Modem Communication Card is fully compatible with devices adhering to the RS-232 standard configured as DTE, which includes most industrial controllers, legacy computers, PLCs, SCADA terminals, and embedded control systems. It supports common serial protocols used in automation environments, such as Modbus RTU, ASCII, DF1, and other proprietary command-based communication frameworks. Physically, the card is designed to interface with standard DB9 or DB25 serial connectors, and electrically, it complies with the EIA/TIA-232 standard.
WOC offers the largest inventory of OEM replacement parts for GE Speedtronic Control Systems. We also provide expert repair services for faulty boards and supply both unused and refurbished boards, each backed by a reliable warranty. Our team of experienced professionals is available 24/7 to support all your OEM and automation requirements. For inquiries about pricing, availability, or repair services, please contact us via phone or email. We’re here to help you keep your systems running smoothly.
What is a Null Modem Communication Card?
A Null Modem Communication Card is a hardware module that allows two RS-232 DTE devices, like computers or PLCs, to communicate directly without a modem. It cross-connects the transmit and receive lines, supporting standard serial communication for industrial and legacy system applications.
What types of devices can be connected using this card?
Devices such as PLCs, industrial controllers, SCADA systems, embedded systems, CNC machines, and older computers can be connected using a Null Modem Communication Card, provided they support RS-232 communication and are configured as DTE devices.
What connector types are used with the Null Modem Communication Card?
Common connector types include DB9 and DB25, though the specific format may vary by card model. Always verify the connector type and pinout before selecting or fabricating null modem cables.
