Which gauge is sometimes used for devices requiring two wires, as an alternative to 22/4?

• A. 16 gauge
• B. 18 gauge
• C. 20 gauge
• D. 22 gauge

Answer: (B)

The main idea here is choosing a conductor thickness that balances current capacity, voltage drop, and practicality for two-wire devices in a low‑voltage alarm setup. When a device only needs two wires, using a thicker conductor than the common 22 gauge helps keep voltage loss low over typical run lengths and makes the wiring more robust.18 gauge is a common middle ground: it’s thicker than 22 gauge, so it has lower resistance per foot, which reduces voltage drop and improves reliability, especially on longer runs or when the device has any modest current draw. It also remains flexible and reasonably easy to install without the stiffness or cost of heavier gauges like 16 gauge.

Thinner options, like 20 or 22 gauge, would have higher resistance and greater voltage drop, which can be an issue for some two-wire devices over distance. A heavier option, such as 16 gauge, is less common for standard two-wire alarm devices because it’s bulkier and more expensive for the typical two-conductor needs. So, 18 gauge hits a practical sweet spot, making it a sensible alternative to 22/4 when only two wires are required.