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MSI - Motion Sensing Interlock

The MSI is designed to control access to rotating machinery that has a run-down time. The MSI relies on the detection of motion via two sensors. Only when both sensors detect zero movement can the key be released. The MSI has been designed to provide the highest level of safety when installed as part of an access control system for dangerous machinery.


The MSI is designed to operate as part of an integrated safety system, controlling access to hazardous areas to motor driven, high risk applications where complete isolation of the power supply is required before access is granted. Two sensors are positioned on the rotating shaft, these are wired into the MSI unit.

When the electric motor is running, the key of the MSI interlock cannot be removed, hence preventing access to the hazardous area. To gain access to the area, the electrical motor must be switched off by turning the key to OFF position. This changes the switches of the electrical supply to the machine to a safe condition. A movement sensing detector sends a signal to the MSI unit once a zero movement of the motor has been stated. A green LED illuminates. By pushingthe green button, the key can now be removed and taken by the personnell to the AI access interlock.

The guard can only be opened when the electrical supply has been switched into a safe condition.The machine cannot be restarted until the door is closed and the key is removed and taken to the MSI movement sensing interlock.

  Type   1 2   3   4   5 6   7      
Part Number MSI -     -   -   -     -        
Example MSI - FS B - F - 3 - 110 A - TBA      

1 Lock portion type FS / Q
2 Material B = Brass, standard
3 Mounting F = Front of board mount with enclosure, standard
4 Secondary lock portion(s) Secondary lock portions are provided for personnel keys,
primary lock portion for the isolation key
1S / 2S = 1 or 2 secondary lock portions respectively
5 Category CAT2 / CAT3 / CAT4
6 Control voltage AC (use for 110 V and 240 V) / DC (use for 24 V)
7 Lock portion symbol FS up to 3 characters / Q up to 6 characters