Alarm EOL Resistors: Single, Double and Triple End-of-Line Wiring Explained

End-of-line resistors allow an alarm panel to interpret defined circuit resistance states. Single, double and triple EOL arrangements can provide different supervision, but their values and wiring are panel-specific. NZ installers should use the chosen panel and detector manuals rather than copying a resistor diagram from another installation.

Understand what circuit supervision measures

The panel evaluates a circuit against programmed resistance ranges or states. A resistor at the correct remote location can help distinguish conditions that a simple unsupervised contact cannot. The interpretation depends on the panel configuration and contact arrangement. Do not assume an open circuit always means alarm or that a short always appears as tamper. Read the exact termination diagram and state table.

Use single EOL deliberately

A single-EOL circuit uses the panel's prescribed resistor arrangement and value. Place the termination where the manufacturer's design requires, normally at the monitored end rather than simply across terminals inside the panel. A resistor in the cabinet can leave field wiring outside the intended supervision. Verify the normal and abnormal resistance states with the selected detector contact and confirm the corresponding panel indication.

Keep double-EOL wiring model-specific

Double-EOL commonly allows additional distinction between alarm and tamper states on a shared circuit, but the actual diagram and state interpretation vary. Follow the panel's prescribed series and parallel arrangement and the detector's contact type. Two resistors installed somewhere on the cable do not establish correct DEOL supervision. Test the detector alarm and enclosure tamper separately and verify the received event labels.

Use the primary technical documentation for this specification alongside the exact proposed configuration.

Check triple-EOL and anti-mask support

Triple-EOL can support additional states such as an anti-mask or fault indication where the chosen panel and detector provide that function. Do not assume a third resistor creates anti-mask capability in a detector that lacks it. Verify input support, programming, contact behaviour and the correct termination diagram together. Confirm how each condition appears locally and at the monitoring provider before accepting the circuit.

Handle retrofit resistor values carefully

Some panels allow selectable termination values, but the supported range and method must come from that exact manual. The RISCO LightSYS+ manufacturer page supplies access to its installer documentation. Use it for the chosen panel revision and match the detector instructions. Do not apply LightSYS+ defaults to a LightSYS2 or another brand automatically. Measure existing circuits appropriately and document values before changing settings.

Record and test every intended state

Create a zone-by-zone record of panel setting, resistor values, contact type and detector model. Under an agreed test window, verify normal, alarm, tamper and any supported mask or fault state, plus restoration. Include controlled open and short tests where the manual and test plan require them. Match received monitoring events to the record. Keep the final wiring diagram with the programming backup for future maintenance.

Apply the design to the actual project

Draw the zone's states beside its wiring diagram. For each intended condition, list the contact position, termination arrangement, programmed setting and expected panel message. Use the panel's own resistance ranges rather than inventing universal thresholds. A detector with alarm and tamper contacts needs its exact diagram; a detector with an additional fault or mask output needs another supported state review. Keep resistor placement visible in the record.

During testing, change one condition at a time and verify restoration before moving on. Obtain the monitoring provider's received event labels where reporting is part of the scope. Record an unexpected result as a fault to resolve, not a passed supervision test because the siren operated once. On retrofit work, document the existing values and any supported programming changes before replacing components. Keep photographs and the final programming backup together. This gives the next technician a traceable circuit design instead of a collection of resistor colours and unexplained zone settings.

Start with an accurate circuit and zone register

Record the panel model and hardware revision, expander addresses, firmware and each zone's programmed function. Associate the physical detector with a unique zone label and its intended area or partition. Note the cable route, any joints and the actual termination arrangement. Photographs of the detector terminals and panel connections help a later technician distinguish a configuration error from a damaged cable. Avoid relying on labels left by an earlier installation without checking them.

Before disconnecting a circuit, agree the test window with the client and monitoring provider. Record the existing condition and isolate equipment according to the manufacturer's procedure. Use resistance measurements on appropriately disconnected, unpowered circuits; an ohmmeter is not a substitute for the panel's live diagnostic display. Restore every circuit and verify normal operation before leaving. Where an installation has undocumented joints or multiple devices on one zone, record the limitation rather than implying individual-device supervision.

Commissioning acceptance checklist

Agree the expected result before testing. Use the installed configuration and retain evidence of each outcome, including a failure that must be corrected. The following checks supplement the exact manufacturer procedures and the approved project design.

Repeat affected checks after a material equipment, software or site change. Keep the test record with the as-built schedule so the next maintainer can understand which configuration passed and which assumptions still need review.

Equipment candidates and specification checks

These are relevant active catalogue candidates for a project review, rather than a universal recommendation or a promise of immediate stock. Use the full product page and current manufacturer information to confirm the supplied variant and its role in your design.

• LPAK-Kit Risco - LightSYS+ Alarm Kit, LCD Keypad, Sirens & batt, 2x or 3x Quad PIR options. Confirm the exact supplied configuration, relevant interfaces and installation requirements before including it in the equipment schedule.
• RP432TMP000A - Risco - Tamper for LightSYS Housing. Confirm the exact supplied configuration, relevant interfaces and installation requirements before including it in the equipment schedule.
• RP432KP0000A - Risco - LightSYS2 LCD Keypad. Confirm the exact supplied configuration, relevant interfaces and installation requirements before including it in the equipment schedule.

Review the relevant Essential Security Supplies equipment range alongside the intended workflow. For further context, read our related installer guide.

Frequently asked questions

Can I use the same resistor value on every alarm panel?

No. Use the selected panel's supported values and prescribed wiring.

Does fitting three resistors add anti-mask detection?

No. The detector, panel input and programming must support the intended state.

Can the EOL resistor simply stay inside the panel?

That may leave field wiring outside the intended supervision. Follow the manufacturer's required remote termination arrangement.

Primary references and technical scope

Use the primary manufacturer or technical reference for the claims it covers. General design guidance does not replace the selected product's installation manual. Confirm current firmware, model variants and the approved project requirements before ordering or commissioning.

Get specification help from Essential Security Supplies

Send your site layout, equipment schedule, intended workflow and any existing model details to Essential Security Supplies for specification help and a project quotation. Identify the functions that must be demonstrated and the interfaces owned by other contractors. Our enquiry route supports a documented equipment review without publishing prices or assuming unverified compatibility.