Which of the following is NOT listed as a UL signaling option?

• A. Direct wire
• B. McCulloh transmitter
• C. One way radio
• D. Fiber optic network

Answer: (D)

UL signaling options describe how alarm signals are transmitted to a monitoring station. These options cover the common paths: a direct wire connection running from the protected premises to the central station, which is the most straightforward wired approach; a one-way radio path, which sends the signal wirelessly in a single direction to the monitor; and the McCulloh transmitter, a specific signaling device historically listed by UL for transmitting through certain lines. Fiber optic network, while capable of carrying signals, is not listed as a UL signaling option in this context, because signaling options in these listings focus on the traditional wired and radio methods. So, fiber optic network isn’t part of the recognized UL signaling options here.