The Allen-Bradley 1785-KE functions as an intelligent, single-slot communication interface module that bridges an asynchronous serial RS-232-C network link with an industrial Data Highway Plus (DH+) network segment. This controller module installs directly into a standard 1771 I/O chassis, enabling computers, modems, third-party analytical instruments, and smart serial peripherals to exchange data directly with programmable logic controllers. It supports cross-network integration across the entire legacy Rockwell automation platform, managing communication streams for PLC-2, PLC-3, PLC-4, and PLC-5 control systems. We distribute this network module as a 100% brand new, original factory component to ensure full electrical compatibility and maximum network uptime.
The following table details the transmission speeds, backplane data, and physical operating thresholds of the 1785-KE module:
| Specification | Details |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Catalog Number | 1785-KE |
| Product Line | PLC-5 / 1771 Chassis System |
| Condition | 100% Brand New Original Factory Stock |
| Module Type | Communication Interface Module |
| Slot Width | Single Slot |
| Integrated Communication Ports | 1 x Data Highway Plus (DH+), 1 x RS-232-C Serial |
| Additional Port Compatibility | 1784-T50 Programming Terminal Interface Ports |
| DH+ Transmission Rate | 57,600 bps Fixed Speed |
| RS-232-C Transmission Rates | 110 to 19,200 bps (Switch-Selectable Ranges) |
| Compatible Controller Networks | PLC-2, PLC-3, PLC-4, and PLC-5 |
| Standard Network Cable Type | Allen-Bradley 1770-CD Coaxial Trunks |
| Backplane Current Requirement | 1.2 Amps at 5V DC |
| Required External Power Supply | None (Draws logic current from 1771 backplane) |
| Maximum Module Capacity | 4 Modules Per System Architecture |
| Operating Ambient Temperature | 0 to 60 degrees C (32 to 140 degrees F) |
| Storage Temperature Limits | -40 to 85 degrees C (-40 to 185 degrees F) |
| Relative Ambient Humidity | 5% to 95% Non-condensing |
| Typical Analog Signal Delays | 29 ms Off Delay (AC) / 30 ms Off Delay (DC) |
| Compatible Mechanical Wiring Arm | 1771-WN Configuration Block |
Immediate High-Speed Serial Integration: The module establishes an automatic protocol handshake that permits slow serial interfaces (110 to 19,200 bps) to write into and read from the much faster 57,600 bps DH+ data ring. This enables legacy supervisory mainframes to manage complex factory floors seamlessly.
Slot-Saving Form Factor: The single-slot configuration saves critical rack space inside standard 1771-A1B through 1771-A4B backplanes. It maximizes remaining slots for high-density I/O modules, thermal couples, or specialized motion control modules.
Conformal Coating for Atmospheric Protection: Industrial environments often introduce airborne moisture, fine conductive particles, and light chemical vapors. The 1785-KE incorporates a professional factory conformal coating across all internal printed circuit boards, preventing micro-corrosion and dendrite growth.
Hardware-Driven Diagnostic Monitoring: A dedicated arrangement of front-panel status LEDs tracks operational diagnostics per channel in real time. Electricians can isolate transmit/receive issues, media connection drops, or baud rate mismatches immediately without opening software diagnostic consoles.
Direct Bus Power Optimization: The hardware completely eliminates the need for external desktop power supplies or complex field-side wiring harnesses. It draws its 1.2 Amp operating current directly from the 5V DC backplane bus pins through the 1771 chassis power supply module.
How do maintenance engineers adjust the serial communication parameters on the 1785-KE hardware?
You configure the RS-232-C transmission rates, parity options, stop bits, and station node addresses manually via physical DIP switches mounted directly on the module circuit board. You must set these configuration switches correctly before sliding the card into the operational 1771 rack slot.
Can I drop this module into any generic slot within a remote 1771 I/O chassis?
Yes. The 1785-KE communication card functions inside any standard 1771 I/O rack slot. The system supports up to four independent 1785-KE interface modules simultaneously across a single control system network, provided the chassis power supply can meet the total 1.2 Amp current demand per module.
Does this interface module require a separate external power input for the DH+ transceiver circuitry?
No. The module operates entirely off internal isolation transformers powered through the standard 5V DC backplane pins. It requires no external pilot voltages or independent electrical loops to maintain full transmission strength across long 1770-CD network cables.
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