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. Spec Value Readers 2 (Wiegand or OSDP) Inputs 4 supervised Outputs 2 relay Communication RS-485 downstream from host panel Power Input 12VDC from host or separate supply 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 SW1 SW2 SW3 SW4 1 ON OFF OFF OFF 2 OFF ON OFF OFF 3 ON ON OFF OFF 4 OFF OFF ON OFF 5 ON OFF ON OFF 6 OFF ON ON OFF 7 ON ON ON OFF 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)