Safety Interlock Classic

Getting Started

The Safety Interlock Classic gives you plug and play expansion to integrate bumper switches, pressure mats and outboard limit switches to protect areas with pinch points and crushing hazards, like pivoting walls or hard edge sliders. The Safety Interlock is wired between the machinery and the Stagehand with simple, pluggable connections to interrupt forward or reverse motion.

This manual will guide you through:

  • Unpacking

  • Installation

  • Powering up

  • Operation

  • Troubleshooting

If you need any help along the way, contact us on our website (, via email (, or by phone (401-289-2942).

What’s Included

In the box you will find:

  • Reference manual (this document)

  • Safety Interlock Classic

  • Two 3-pin XLR jumpers

  • Two limit jumpers

If any of these parts are missing, please contact us.

If you ordered any bumper switches or pressure mats those items are packaged separately.


The Safety Interlock Classic is a 3U rack mountable device with 4 mounting holes. Check out the features below.

  1. Status indicators

  2. Forward Limit Connections

  3. Reverse Limit Connections

  4. Forward safety sensor connections

  5. Reverse safety sensor connections

  6. Emergency stop input and output


The Safety Interlock Classic is a 3U rack mountable case designed to fit in a standard 19” rack. It is not required to be rack mounted, feel free to place it on the operator desk or with the Stagehand motion controllers.

A key point to note during installation is that the Safety Interlock Classic will need to be connected between the machine and the Stagehand motion controller.

Powering Up

After the Safety Interlock is installed, it is time to power it up and test that the bumper switches, pressure mats, and/or limit switches are working correctly. The Safety Interlock Classic requires 24VDC, provided from the Showstopper Base or Showstopper Hub. The Showstopper cable has 5 pin XLR style connectors (DMX):

Connect a Showstopper Cable from the Showstopper Base to the E-Stop Input. Connect another Showstopper cable from the E-Stop output on the Safety Interlock to the Stagehand.

The Stagehand Motion Controller may also be connected directly to the Showstopper Base or Showstopper Hub

Limit Connections

The Stagehand AC Motion Controller monitors Forward and Reverse limit circuits. In order for the Safety Interlock Classic to interrupt these signals, the Forward and Reverse limits need to feed through the Safety Interlock.

Connect the Forward and Reverse Limits from the Stagehand to the Safety Interlock Classic and then on to the machine with ML-1 extension cables.

Sensor Connections

The safety interlock adds additional support for 4 wire safety circuits (e.g. bumper switches and pressure mats). A 4 wire safety circuit, when used in conjunction with the safety relay inside the Safety Interlock Classic allows monitoring for the following four conditions:

  1. Disconnected - the safety relay sends out test pulses through the sensor and expects the signal to return. If that signal does not return the safety relay will go into a faulted state and disallow any further motion.

  2. Shorted - if a wire has been crushed by equipment or cut the safety relay will go into a faulted state.

  3. Cross Circuit - if the signals get crossed and the test pulse comes back on the opposite channel the safety relay will go into a faulted state.

  4. Good - if none of the above conditions occur the safety relay will not prohibit any movement.


Once powered up, the Safety Interlock Classic is operational. If all of the connections have been properly made, the entire system is powered up, and none of the sensors or limit switches are activated, the Safety Interlock Classic is actively doing its job. To verify this, the three indicator lights on the face should all be illuminated. Other than connecting or disconnecting any limit switches or sensors, there should be nothing else that needs to be done to the Safety Interlock itself.


When encountering an issue with the Safety Interlock Pro, the first thing to check would be that none of the limits or sensors are activated. If they are not, the next thing to check would be that all of the cables or jumpers are connected properly. If all connections are made properly and none of the sensors or limits are activated it would be best to make sure that none of the cables have been cut or damaged.

Common Problems

The issue that is most often encountered is leaving an open connection. All connections on the back of the interlock need to have a physical cable or a jumper plugged in. Making sure that either the cables or the jumpers are seated properly is also important. It is common to mix up the sensor input and outputs in the forward and reverse direction.



No indicator lights illuminated

Check E-Stop status

Only Power and REV safety sensor indicators illuminated

Confirm no FWD limit is activated

Confirm no FWD sensors activated

Confirm they are plugged into correct direction

Confirm Sensor Jumpers are installed

Only Power and FWD safety sensor indicators illuminated

Confirm no REV limit is activated

Confirm no REV sensors are activated

Confirm they are plugged into correct direction

Confirm Sensor Jumpers are installed

Only Power indicator illuminated

Confirm no limit is activated FWD and REV

Confirm no sensor is activated FWD and REV

Confirm they are plugged in to correct corresponding direction

Technical Support

If you get stuck, we are here to help. The best way to get in touch with a tech expert is via email, even during normal business hours, because most days we are on the shop floor and may not be near the phone. There is someone in the office from 8:30a-5pm EST Monday-Friday, and they will return an email or phone call quickly. After hours, when most tech support issues arise, we have a crack team monitoring email and voicemail who will respond quickly to help get you moving.


  • Inputs for both Forward and Reverse safety sensors (bumper switches or pressure mats)

  • Pass through connections for Stagehand Limit Switch signals

Electrical Specifications



Emergency Stop Input


Emergency Stop Output


Safety sensor (FWD & REV)

24VDC, 130mA max


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