MR52 — Downstream Reader Interface

Overview

The Mercury MR52 is a downstream reader interface module used to expand a Mercury panel with additional reader ports. It adds 2 readers and 4 supervised inputs per module. Typically used with an EP1502 or similar host controller to support additional doors without a full second panel.

DIP Switches

The MR52 uses DIP switches to set its downstream RS-485 address relative to the host panel. Multiple MR52 modules can be chained from a single host.

Address 0 (all OFF) is not valid — each MR52 must have a unique address. SW5–SW8: Reserved — leave OFF.

Wiring Notes

• Downstream RS-485: Connect the MR52 A(+)/B(−) to the downstream RS-485 port on the host Mercury panel (not the upstream network port). This is a separate bus from the host-to-controller RS-485.

• Termination: Place a 120Ω termination resistor on the last MR52 in the chain.

• Power: 12VDC — can share the host panel power supply if within budget, or use dedicated 12V supply for longer runs.

• Readers: R1 and R2 — connect same as a standard Mercury panel reader port (Wiegand or OSDP).

• Inputs: 4 supervised inputs — typically used for door contact (Input 1) and Rex (Input 2) for each reader, plus auxiliary inputs.

Common Use Cases

• Adding a second reader to a door (exit reader) where the host panel reader port is already used

• Expanding a single-door panel to handle additional monitoring points without adding a full panel

• Connecting readers in a remote location (elevator lobby, parking gate) with a longer RS-485 run

Resources

• MR52 Installation Guide (HID/Mercury)

• Mercury Installation Assistant Utility (IAU)