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Definition of Ancillary Device

CAN/ULC - S536-19

3.7 A device which has a life-safety application, and is connected to the fire alarm system, but is not part of the fire alarm system.

E.V.S. SM-001 - Approved application is to test specific field devices and system wiring as listed by both UL and ULC. 

Have a question as to what you can or cannot do with the Electronic Verifying Switch (EVS)?
See our FAQ section below!

  • Is the Electronic Verifying Switch (EVS) an ancillary device or a fire alarm device?
    The EVS is 100% an ancillary device. UL/ULC determined and declared it to be an ancillary device, as it does not detect or signal a fire situation, even though it is connected to the fire alarm system.
  • Is replacing an existing end of line plate with an EVS plate considered a modification to your fire alarm system?
    NO, our EVS is just another plate to mount the circuit resister on. Which is the actual end of line device. Therefore, no modification to system and no permits required as you are not changing devices.
  • If I replace my existing end of line plate with the EVS, am I required to have a third-party verification?
    NO, you are not modifying your existing system, as you are not changing the end of line resistor which is the device. The EVS is just a holding plate for the resistor.
  • Can the EVS be installed to short test a conventional fixed temp non-restorable heat detector?
    YES, and it has been approved and listed by UL/ULC to do just that. CAN /ULC-S536 ( is a visual inspection. Otherwise, you would have to take down every device, every year and check the wiring connections on them as well. Which is not the intent of the code and why, UL/ULC approved the EVS in this application.
  • Does the EVS connect directly onto the conventional fixed temp non-restorable heat?
    Yes, code requires non-restorable heat detectors to be electrically tested at the wiring connections on the device. UL/ULC has approved and listed the EVS to be directly connected as per our installation instructions. As introducing a simulated short can be done in a verity of ways and because the EVS is a UL/ULC listed ancillary device and NOT a fire alarm device, it is not required to be supervised in this instance.
  • Can the EVS be used to test smoke detectors?
    100% NO, smoke detectors must be tested as per proper testing requirements laid out in CAN/ULC-S536.
  • Can the EVS be used to test rate of rise heat detectors?
    100% NO, rate of rise heat detectors must be tested as per proper testing methods laid out in CAN/ULC-S536.
  • Is the EVS a fire alarm device?
    NO, UL/ULC has determined the EVS to be an ancillary device and approved it as an ancillary device.
  • Can the EVS be used to short test fault isolators?
    Yes, as approved and listed to do so by UL/ULC. The EVS is connected to the isolated side of the fault isolator, allowing for a short to be introduced and confirmed at panel, then you can operate a device on the source side and confirm it’s operation.
  • Can the EVS be used to test sprinkler devices such as flow alarms, low pressure switches or tamper switches?
    100% NO, all sprinkler devices must be mechanically tested as required by code.
  • Can the EVS be used to bypass any alarm or supervisory input?
    No bypassing an input would require a supervisory trouble condition at the panel and proper testing does not allow for a device to be bypassed during testing.
  • Can the EVS be used on an AC amplifier speaker circuit?
    No, if speaker outputs operate on AC voltage you cannot, as our EVS is only rated for DC voltage.
  • Can the EVS be used on a fire alarm system with a max current of 400mA?
    Yes, UL/ULC has tested and approved the EVS up to a Max Inrush Current of 1800mA and a Normal Current of 350mA. Both are well above any fire alarm panel requirements.
  • Can I connect an EVS to an unsupervised output?
    At this time we do not have any listing for this application. However, if you do, make sure you do not exceed the EVS max ratings listed in our instructions.
  • Does the EVS allow me to test the circuit voltage without removing the plate from the wall?
    Yes, you can simply insert your meter leads into the voltage ports on the front of the EVS plate to get your voltage readings.
  • Why does the EVS only have a maximum voltage rating of 40vDC?
    40vDC is the maximum voltage allowed on a low voltage system. Fire alarm systems are classified as low voltage and therefore can not exceed 40vDC. Most fire alarm systems operate between 26 & 28vDC. Which is well below our 40vDC listing.
  • Can the EVS be used to test in-suite isolators?
    Yes, the EVS is to be installed on the isolated side of the isolator for the in-suite horn. When shorted in a supervisory state or in an alarm condition the isolator will isolate that suite’s horn without affecting the rest of the audibles. In this application the short while in alarm, will not damage our Electronic Verifying switch as the isolator removes the power once shorted. Again, approved and listed by UL/ULC for this test. Note: the EVS just introduces the short, the in-suite isolator (FA device) is what you are testing for proper operation.
  • What other uses can the EVS be used for?
    During the early days of R&D we submitted potential applications and drawings with UL/ULC with the intent of utilizing the Electronic Verifying Switch for additional testing applications. After review UL/ULC only approved and listed the applications currently in our installation instructions.
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