Electromechanical Interlocks - Time Delay Unit (TDKRU)

TDKRU stands for Time Delay Key Release Unit, and protects against scenarios where hazardous energy needs time to neutralize. 

The Type TDKRU is designed to permit removal of the initially held (or secondary) interlock key after insertion of a primary key and the elapse of a predetermined time delay. The TDKRU is comprised of two key interlocks, a timing device, a solenoid, and a signal light for indication.


The photograph illustrates the TDKRU in the normal position - a key is retained in the secondary interlock. A primary or initiating key is introduced to start the time delay. After a predetermined delay, the solenoid is energized (the LED signal lamp illuminates to indicate the energized state) – permitting the secondary key to be rotated and withdrawn for further steps in the overall interlock scheme. After removing the secondary key, the primary key is trapped in the TDKRU. Should the primary key be rotated and removed during the time delay period, the timing device instantly returns to its original position.



  • Mounting Options – available housed in a fiberglass reinforced polyester enclosure or unhoused with cover plate only.

  • Timing Device – the time delay can be any length of time from 1 second to 30 minutes. Note: The duration of the time delay must be set by the customer during installation of the TDKRU. Two timers are available: 1) 1-300 seconds, 2) 3-30 minutes. The correct timer must be specified at the time of order.

  • Solenoid voltage – 120VAC, 24VDC, 48VDC, or 125VDC

  • Reference our wiring guidelines on our website as needed

trapped key interlocks

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                       (800)438-2442 | FAX (330)497-4400 | sales@kirkkey.com


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