What This Article Covers
This guide explains how auxiliary switch monitoring works on electric strikes used in commercial access control openings. If you are a security integrator, commercial contractor, or facility manager specifying or troubleshooting an electrified opening, understanding what a latchbolt monitor and locking cam monitor actually report — and what they do not — will save you callbacks, failed inspections, and misdiagnosed service calls.
What Is an Auxiliary Switch on an Electric Strike?
An auxiliary switch is a small secondary electrical contact built into an electric strike body. It does not control the strike. Instead, it reports a condition back to an access control panel, alarm system, or building management system. The switch changes state — open or closed — depending on the mechanical position of a component inside the strike.
Most commercial electric strikes offer one or both of the following monitoring types:
- Latchbolt monitor: Reports whether the latch bolt from the lockset is engaged in the strike keeper.
- Locking cam monitor: Reports whether the strike's internal locking cam is in the locked or unlocked position.
These are two different things, and confusing them is one of the most common specification errors on monitored openings.
Latchbolt Monitor vs. Locking Cam Monitor: The Difference That Matters
Latchbolt Monitor (LCBMA)
A latchbolt monitor detects whether the door's latch bolt has actually projected into the strike. This tells you the door is physically closed and the latch is engaged. It does not tell you whether the strike is locked or unlocked.
In practical terms, a latchbolt monitor answers: Is the door closed and latched?
This is the signal your access control system or alarm panel uses to detect door-ajar conditions. If a door is propped open, the latchbolt monitor changes state and your panel can alert security staff or trigger a door-held-open alarm.
Locking Cam Monitor
A locking cam monitor reports the position of the strike's internal keeper or cam — whether it is in the locked (holding) position or the unlocked (released) position. This tells you whether the strike has responded to a command from the access control system.
In practical terms, a cam monitor answers: Did the strike actually unlock when commanded?
This is the signal used to verify that a strike is functioning correctly after receiving a credential read or remote release command. It is particularly valuable for compliance documentation in healthcare and institutional settings where door activity logs must be complete.
Why Both Monitors Together Changes the Picture
When a strike includes both latchbolt and cam monitoring, your access control panel can distinguish between four meaningful states:
- Door closed and latched, strike locked — normal secured condition
- Door closed and latched, strike unlocked — access granted, occupant has not yet opened the door
- Door open, strike locked — door is ajar or forced; latch not engaged
- Door open, strike unlocked — door legitimately in use after credential event
A strike with only one monitor type gives you only half this picture. Specifying the wrong monitor — or omitting monitoring entirely — reduces your access control system to a simple electric lock with no feedback loop.
Where Dual Monitoring Gets Specified
Combined latchbolt and cam monitoring is not overkill for every opening. Understand where it earns its place in the hardware set:
- Healthcare facilities: Patient room doors, pharmacy access points, and behavioral health unit entries where door status must be logged continuously for regulatory compliance and staff safety.
- School and university openings: Exterior entries and secure corridor doors where door-held-open alarms and access audit trails are required by security policy or district mandate.
- Retail and commercial back-of-house: Loading dock entries and storage rooms where a door left ajar creates both security and loss-prevention exposure.
- Industrial and manufacturing: Server rooms, electrical vaults, and controlled-access areas where proof-of-lock status must be logged for compliance audits.
Fail-Secure vs. Fail-Safe: What the Monitor Reports When Power Drops
Monitoring does not change the fail-state behavior of an electric strike, but it does interact with how your panel interprets a power loss event.
On a fail-secure strike, power loss leaves the keeper engaged — the door stays locked. Your cam monitor will report the locked state. Your access control panel should be configured to recognize this as a normal power-loss condition, not a forced-door alarm.
On a fail-safe strike, power loss releases the keeper — the door becomes unlatched. The cam monitor will report the unlocked state. If your panel is not programmed to expect this on a fire alarm drop or power event, you will generate nuisance alarms at every power interruption.
Important: Fail-safe electric strikes cannot be used on fire-labeled openings. Only fail-secure configurations maintain positive latching when power is removed, which is required to preserve the fire rating of the door assembly. If you are specifying an electric strike on a fire-rated opening, confirm the strike carries a fire listing and is configured fail-secure.
Voltage Selection and Wiring the Auxiliary Switch
Most commercial electric strikes with monitoring are available in 12 VDC or 24 VDC configurations. The auxiliary switch outputs are typically dry-contact SPDT (single-pole, double-throw) circuits, meaning they can be wired normally open or normally closed depending on how your access control panel expects to receive the signal.
Common field wiring mistakes that defeat monitoring:
- Leaving the auxiliary switch terminals unwired entirely — the strike operates but the panel receives no status feedback
- Wiring the monitor in parallel with the strike power circuit instead of as a separate signal loop
- Selecting the wrong normal state (NO vs. NC) at the panel, causing the system to read locked as unlocked and vice versa
- Routing monitor signal wiring through the same conduit as high-voltage circuits, introducing noise that causes false state changes
If you are routing power through the door itself — for example to an electrified lockset or exit device — the method of power transfer must be planned before rough-in. Electric hinges and flexible door cords are the two standard approaches for commercial openings. The monitoring signal wires must be included in that transfer path, not added as an afterthought at close-out.
Stainless Steel Finish and Corrosion Considerations
Electric strikes in monitored openings are often specified in US32D (satin stainless, BHMA 630) finish. This is not purely aesthetic. Stainless steel resists the cleaning chemicals used in healthcare and food service environments, where electric strikes near service entries are regularly exposed to moisture and detergents. A monitored strike that corrodes internally can produce intermittent false alarms that are difficult to diagnose without pulling and inspecting the unit.
Choosing the Right Electric Strike for a Monitored Opening
When you are specifying an electric strike with monitoring for a commercial opening, the decision checklist looks like this:
- Is the opening fire-rated? If yes, you need a fire-listed, fail-secure strike.
- What lockset type is on the door — cylindrical, mortise, or rim panic? Strike body geometry must match.
- Does the access control system require latchbolt status, cam status, or both?
- What voltage does your panel supply — 12 VDC or 24 VDC?
- What is the expected preload on the strike — is door hardware or building pressure pushing against the keeper when locked?
- What finish is required for the environment?
DoorwaysPlus carries electric strikes with single and dual monitoring configurations from trusted commercial hardware lines. If you are building out or retrofitting a monitored access control opening and need help matching the strike to your panel and lockset combination, the team at DoorwaysPlus can help you get the specification right before the door ships.