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Diagnosing EN 04 code on APeX controller

Updated: Oct 17, 2023

EN codes are the APeX controllers primary way of signaling an entrapment condition with the system. These codes range from EN 00, to EN 14. We will discuss each of these codes, their meanings, and possible solutions in periodic blog posts. Comments and questions are welcomed and encouraged to help you understand the system you are working on as thoroughly as possible.

The EN04 code is activated any time the APeX board gets a signal from the "Fire Dept" input. This set of terminals is located on the left side of the board below the "COMM LINK" connection for primary/secondary or bi-parting gate communication. You can find our blog post on any issues related to the "EN03" error for a bi-parting setup here.


When an EN 04 error occurs, a lockout condition is present due to an input on the "FIRE DEPT" terminals on the APeX board. This input should be reserved for emergency vehicle and personnel access only. Siren Operated Sensors (SOS), Knox Lock, EVAC transmitter/receiver system, or other emergency vehicle access device. Using this input for keypads, loops, radio receivers, or other normal use access devices WILL result in the gate staying open and a lockout condition EVERY TIME the device is used, and will require a reset to start operating normally again.

When triggered, this input will display "EN 04" on the APeX display, and will have the "LOCKOUT" LED lit preventing movement of the gate until a reset is performed. This is a required feature of all automatic gate operator control boards to prevent hinderence of emergency personnel from accessing patients, suspects, fires, etc. as the gate will stay open allowing more vehicles as necessary or the free egress of vehicles and personnel when leaving to a hospital for example.

To reset this error code and return the gate to normal operation, check with the property manager or owner to make sure that emergency services did gain access and, in the case of the Knox Lock, that they turned the key back to "Normal Operation". Check the emergency access device to ensure that it is functioning properly and didn't malfunction causing a false signal. Check wiring to ensure no damage or exposed copper made contact to send a false signal.

Once all devices have been checked and found to be properly functioning, press the "RESET" button on the bottom of the control box, or the "STOP" button next to the display on the APeX board; this should reset the error. You can now test run the gate system and check for normal operation.

If the problem persists after checking these devices and wiring, contact your installing dealer, distributor, or Rotary Gate Systems for further troubleshooting or replacement parts.

All error codes, and diagnostics can now be managed remotely with the Rotary IQ. This system is designed to work with all gate operators using the Linear APeX circuit board from 2008 to present and allows installing dealers a glimpse at what is happening with a gate operator before making a trip on site, saving time and money.

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