Honeywell 621-9928R Serial Link Selector Module

The Honeywell 621-9928R is a Serial Link Selector (SLS) module designed for use in Honeywell IPC 620/621 Redundant Logic Manager control systems. The module manages serial communication path selection between redundant processors and associated communication links. It is installed as a double-width module and provides switching control under the supervision of the Redundancy Control Module (RCM).

Function in Redundant Control Systems

The Serial Link Selector Module forms part of the communication architecture used in redundant IPC 620/621 systems. Its primary function is to connect external serial communication paths to the currently active processor while maintaining coordination with the system's redundancy management strategy.

Selection and switching operations are controlled by the Redundancy Control Module (RCM), allowing the communication path to follow the active controller within the redundant pair.

Module Configuration

The 621-9928R is a double-wide module that occupies slots B and C of a designated I/O card file. This mechanical arrangement provides space for the serial link switching circuitry and associated terminal connections.

Two detachable terminal modules are provided on the front of the unit, simplifying field wiring and module replacement procedures.

Status Monitoring

The module includes onboard LED indicators that display processor selection status. These indicators assist maintenance personnel in verifying which processor currently controls the active serial communication path.

Visual indication can simplify troubleshooting during controller switchover events or redundancy diagnostics.

Terminal Connections

Field connections are made through front-mounted detachable screw-terminal assemblies. The design uses two 12-position detachable terminal modules, providing convenient access for installation and maintenance activities.

Technical Specifications

Application Considerations

The 621-9928R is intended for systems that employ processor redundancy and require controlled selection of serial communication links. Proper operation depends on integration with the associated IPC 620/621 redundancy architecture and Redundancy Control Module functions.

Because communication path selection is coordinated by the redundant control platform, the module should be matched to the intended IPC system configuration during maintenance or replacement activities.

Frequently Asked Questions

Q: What is the primary purpose of the 621-9928R module?
A: The module selects and routes serial communication links within a Honeywell IPC 620/621 redundant control system, allowing communication paths to follow the active processor.

Q: Where is the 621-9928R installed?
A: The module is installed as a double-width assembly occupying slots B and C of a designated I/O card file.

Q: How can maintenance personnel determine which processor is active?
A: The module includes onboard LED indicators that provide status information related to processor selection.