Controlled Access with

Solenoid Locking   


Independently Certified       

for use in up to SIL3 Cat. 4 PLe


The Heavy Duty guard lock module is used to manage activities and for controlled access with solenoid locking. This module within the amGard pro range can be fitted to any actuator or head combination and can be used in conjunction with trapped keys, escape release and push buttons.


How does the Guard Lock Operate for Controlled Access?

Power to Unlock – Standard Solenoid Controlled Lock – (SL411)


“Recommended on machines with run-down cycles”




Dual Channel Safety on Guard Locking


On supplying power to the solenoid, the unit becomes unlocked and safety circuits are opened.

This is the recommended set up for most machine guarding applications.

1.   Gate Shut and Locked – Standard Power-to-Unlock LOK variants have two pairs of normally closed safety circuits and two normally open monitoring circuits; one on the head and one on the solenoid. In this state the machine is running, the solenoid is de-energised, and the actuator is trapped in the head.


3.   Gate Opened – When the actuator is removed from the device (or trapped key removed if present), the head plunger is sprung against the head safety circuits and monitoring switches (causing the red LED to switch on).

2.   Gate Unlocked – When a Machine Stop Command is requested and logic completes a run-down time, the solenoid inside the device will energise. This causes a rotational actuator to depress the safety circuits and monitoring circuits on the guard locking (and cause the yellow LED to switch on).


4.   Escape Release – Activation of an escape release will actuate the head safety circuits and monitoring switches causing the red LED to activate.



SL411   |   SR411   |   ZL411   |   ZR411   |   SL421   |   SR421   |   SL431   |   SR431   |   SL111   |   SR111   |   SLP11   |   SRP11   |   SL211   |   SR211


Non-safe Monitoring of this device is achieved with two Normally Open switches which are linked to LED illumination.

The Yellow LED indicates when the dual safety circuits for Safety on Guard Locking are Opened (when unlocking the device).

The Red LED indicates when the dual safety circuits for Safety on Guard are Opened (when accessing the safeguarded space).

Mechanical Override



Solenoid modules can be fitted with a special key driven Auxiliary Override facility for use in the event of power failure from outside the safeguarded space.

The key is not kept in the device and is only used when the solenoid must be overridden.

An Emergency Override knob provides an always present means to override the locking mechanism from outside the safeguarded space.

The Highest Level of Safety



Alternative Variations of Controlled Access with Solenoid Locking

Power to Lock – Solenoid Controlled Lock – (SL461)


In Power to Lock devices, on supplying power to the solenoid, the unit becomes locked. This is not the recommended set up for most machine guarding applications, however it allows access and exit in the event of a power failure.

Power to Lock devices have Safety on Guard Only which means that safety contacts will only open when the guard is opened, not when an unlock request is sent.


SL461   |   SR461   |   ZL461   |   ZR461   |   SL161   |   SR161   |   SLP61   |   SRP61

Power to Unlock with Unmonitored Solenoid – (SL416)

On supplying power to the solenoid the unit becomes unlocked, however only a single monitoring contact is closed.

This is a popular configuration for where the solenoid performs a process control rather than safety function.

A special key driven override facility is included to unlock the unit in the event of a power failure.



SL461   |   SR461   |   ZL461   |   ZR461   |   SL161   |   SR161   |   SLP61   |   SRP61

Archive of Guard Locking Variants