In his latest post, Mark Kuhn addresses a common question that comes up during code review…What’s the purpose of an RX switch in the door-mounted hardware?

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I’m writing today about an often-misunderstood piece of electronic hardware…the request-to-exit switch, commonly called an “RX” switch.  For the purposes of today’s post, I’m talking about an RX switch that is inside of the hardware that is mounted on the door.

Now before I dive into this post, I know that RX switches in the door hardware have many uses and there are some cases where the RX switch is part of a “special locking arrangement.”  Some of those examples are:

When used in the situations listed above, the RX switch does play a part in ensuring code-compliant egress.

Note:  There are also sensors and push buttons that are sometimes referred to as REX sensors or REX switches, as they facilitate egress.  But as I mentioned before, this post specifically addresses RX switches inside of the door-mounted hardware.

An RX switch can also be used to turn pieces of hardware on and off.  The most common example of this is when a door has an automatic operator.  An RX switch in a panic device can be used to activate and deactivate the actuators for the auto operator. Dogging the panic hardware closes the contact of the RX switch inside, turning on the actuator buttons that control the operator.  When the panic is undogged, the actuators are no longer active, which prevents the auto operator from trying to open the door when the door is latched and unable to open automatically.

You get the idea; the RX switch has a lot of uses.  However, we often have questions about RX switches during the code review process, even when the switch has no impact on a building occupant’s ability to exit.  The reason the switch may be flagged during code review is because the reviewer believes that the switch is used with hardware that may impact egress.

The fact of the matter is, most of the time the RX switch is just there to monitor the opening, not to control the opening.  These doors would fall under what Lori refers to as “normal locking arrangements.”  The hardware in question would still always allow free egress.  But the notes we receive from the plan reviewers usually reference the “Unlatching” section of I-codes, “egress shall require not more than one motion…” or they may reference the “Door Operations” section, “egress doors shall be easily openable from the egress side without key or special knowledge or effort…”

So, what is the purpose of the RX switch in a normal locking arrangement?  Good question! The RX switch may be part of the detection system that monitors the egress side of the opening and alerts the system of an “authorized exit.”  This means that a person has approached the door from the inside to exit through the door, and the door was not forced open from the outside (or secure side).

The RX switch works together with a door position switch (DPS).  If the DPS shows that the door has opened, and the access control system has not received a signal from the RX switch, it assumes that the door has been forced open.  This may cause an alarm to sound, or may send a signal to security personnel.  If the system receives a signal from both the RX switch and the DPS switch, then it recognizes an authorized egress, also known as a “legal release.”

I know that the comments will probably be filled with MANY other uses for an RX switch, but I’ve tried to hit the highlights.  I hope I’ve done an adequate job of explaining some of the uses for this small but important part of an electronic access control system and give us a better understanding of the request-to-exit switch.

And to help clarify the code requirements for systems that include an RX switch for monitoring the use of a door, a section was added to the 2021 I-Codes and revised in the 2024 editions:

1010.2.9 Monitored or recorded egress, and access control systems. Where electrical systems that monitor or record egress activity are incorporated, or where the door has an access control system, the locking system on the egress side of the door shall comply with Section 1010.2.10, 1010.2.11, 1010.2.12, 1010.2.13, 1010.2.14 or 1010.2.15 or shall be readily openable from the egress side without the use of a key or special knowledge or effort.

This section clearly states that a door is permitted to have electrified hardware with an RX switch monitoring egress, or an access control system limiting access.  These doors must either be readily openable from the egress side, or they must comply with one of the code sections addressing special locking arrangements.

Any questions?

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