Support for EOL resistors for trouble detection?

[eddyg]

Any plans to support (optional) monitoring of zones for tampering/trouble via end-of-line resistors? (All of my zones have a 1 kΩ resistor in the loop, and have been quite handy in detecting problems over the years.)

[taconsultingllc]

Thank you for your question; it’s a valuable consideration and one I prioritized during the design process for the Hornet Nest Alarm Panel. This panel is optimized specifically for no End-of-Line (EOL) and single EOL resistor configurations, which are commonly used in professional security systems, including one I previously owned.

In a single EOL configuration, the panel effectively supports core features such as standard zone monitoring and violation alerts. However, please note that it does not support short-circuit detection between the panel and the sensor in this setup.

The decision to focus on single EOL compatibility ensures a streamlined setup for users who prioritize essential security features without added complexity.

Normally Closed Loops – No EOL

_{(Fully Supported by Hornet Nest)}

This is the simplest circuit and also the one with least protection from wiring faults. In this configuration, the circuit is not supervised for open or short circuit conditions. This is simply a normally open contact placed between Z and COM terminals.

• Zone normal or short circuit: 0Ω
• Zone violated or open circuit: ∞Ω

Wiring diagram for Normally Closed (no End-of-Line resistor) circuit.

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Single End-of-Line Resistor

_{(Partially Supported by Hornet Nest)}

This is the default circuit configuration. As the name implies, it uses only one EOL. The circuit is supervised against a short circuit, but there is no differentiation between a violated zone and an open circuit.

• Zone normal: 5600Ω (for DSC control panels)
• Zone violated or open circuit: ∞Ω
• Short circuit: 0Ω _{(Not Supported by Hornet Nest)}

Wiring diagram for single End-of-Line resistor circuit.

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Double End-of-Line Resistor

_{(Not Supported by Hornet Nest)}

This is the most secure wiring type. With double End-of-Line resistor wiring, the control panel is able to differentiate between four conditions:

• Zone normal (contact closed): 5600Ω (for DSC control panels)
• Zone violated (contact open): 11,200Ω (for DSC control panels)
• Open circuit: ∞Ω
• Short circuit: 0Ω

Wiring diagram for double End-of-Line resistor wiring.

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Source: Tremtech Blog - How to Wire Security Alarm Zones

[eddyg]

Thanks for the quick reply!

It's a bummer that short-circuit detection isn't supported. We were having some work done and a contractor (unknowingly) put a nail through one of the alarm wires. Without short-circuit detection, this would make the window/door seem like it was always closed — but with it, the zone indicated "TROUBLE" right away.

Looking at the difference between "no EOL" and "single EOL", it seems the Hornet Nest "tolerates" a single EOL resistor in the loop, but doesn't benefit from its presence?

[taconsultingllc]

"Looking at the difference between "no EOL" and "single EOL", it seems the Hornet Nest "tolerates" a single EOL resistor in the loop, but doesn't benefit from its presence?"

You are correct in your assumption. The Hornet Nest was primarily designed to be compatible with single EOL systems, as they are the most common configuration in current installations. I have tested the zone functionality with EOL resistances greater than 10kΩ, but the system does not derive any functional benefit from the presence of the EOL resistor.

Initially, I had planned for the Hornet Nest to support both EOL and double EOL (DEOL) configurations. However, given the variety of resistance configurations used by different manufacturers and the likelihood that many users would not require such complexity, I opted to focus on supporting no EOL and single EOL systems. This decision was made to keep the wiring process straightforward for most users.

As I’ve mentioned in various forums, I’m always open to product improvement suggestions and have already begun incorporating several of those into the latest revision, which will ship during the campaign. You are only the second person to inquire about EOL configurations. If there is sufficient demand for such support, I would certainly consider including it in a future revision or potentially offering it as a separate product.