Which gauge is sometimes used for devices that require two wires, instead of 22/4?

• A. 16 gauge
• B. 18 gauge
• C. 20 gauge
• D. 24 gauge

Answer: (B)

When a device only needs two conductors, choosing a cable with a thicker single pair helps carry the current more reliably and minimizes voltage drop over distance. Eighteen-gauge two-conductor cable is a common choice in alarm installations for these two-wire devices because it provides lower resistance than 22-gauge, improving performance on longer runs or for devices that draw more current.

Using eighteen gauge over 22/4 isn’t about more wires; it’s about the capability of those wires to handle the load with less voltage loss. The other gauges mentioned are either thinner or thicker and aren’t as typically used for standard two-wire low-voltage devices: sixteen gauge is quite thick and stiff, often reserved for higher-current power runs; twenty gauge is thinner and may suffer more voltage drop on longer runs; twenty-four gauge is even thinner, with higher resistance, making it less suitable for most two-wire alarm devices.