Mercury MR16IN and MR16OUT: When You Need More I/O Than Your Controller Has

Mercury EP series controllers are powerful, but they have a finite number of inputs and outputs. When you run out of I/O — and on larger installations, you will — the MR16IN and MR16OUT are how you expand.

The MR16IN adds 16 monitored inputs. The MR16OUT adds 16 relay outputs. Both connect to your existing Mercury controller over RS-485 and show up in your access control platform as additional points. No additional licensing. No new controller. Just more I/O.

MR16IN: 16 Programmable Inputs

The Mercury MR16IN-S3 is a 16-input multi-device interface panel. Each input circuit can be individually configured for:

• Operation: Normally open or normally closed
• Supervision: Supervised or non-supervised monitoring
• EOL Detection: End-of-line resistor supervision with range-based detection
• Relay Outputs: 2 dedicated programmable Form C relays (5A @ 28 VDC)
• Fail Mode: Configurable fail-safe or fail-secure operation

Use cases: alarm zone monitoring across a large building, elevator floor tracking, HVAC status monitoring, interlock monitoring for mantraps, auxiliary sensor monitoring (glass break, motion, door prop). If you have 16 things that need to report status back to your access control system, this is the board.

MR16OUT: 16 Relay Outputs

The Mercury MR16OUT-S3 is the output counterpart. It gives you 16 Form C relay outputs, each rated at 5A @ 28 VDC. Every relay is independently programmable for fail-safe or fail-secure.

Use cases: elevator floor control (one relay per floor), parking gate control, lighting automation triggered by access events, HVAC zone control, interlock sequencing, lockdown control for multiple doors from a single command.

How They Connect

Both modules connect to any Mercury EP series intelligent controller (EP1502, LP1502, MP1502, EP2500, etc.) via RS-485 shielded twisted pair, up to 4,000 feet from the controller. They support AES-128/256 encrypted communication with embedded cryptographic memory for data at rest. See our Mercury MP1502 guide for more on the head-end controller.

Up to 32 SIO modules can be multi-dropped on a single RS-485 port. That means you can mix and match MR16INs, MR16OUTs, MR52s, and MR50s on the same bus as your reader interfaces — giving you massive I/O expansion without adding controllers.

The Scenario That Brings You Here

You're probably reading this because you have one of these situations:

• Elevator control: Your building added a floor or wing, and you need elevator control relays for the new floors
• Alarm integration: Your security director wants alarm monitoring points integrated into the access control system instead of running a separate intrusion panel
• Parking control: You're doing a parking garage with gate arms and lane indicators that need relay control
• Failed board: A board failed and you need a replacement before the end of the week

In all four cases, the answer is the same: buy the board direct, ship it today, drop it in.

Why Buy from Rapid Security Hardware

We stock MR16IN-S3 and MR16OUT-S3 hardware as inventory permits. Check each listing for current condition, shipping options, guarantee details, and compatibility notes.