Final answer:
A security guard on a vehicle patrol would most likely use a two-way radio to communicate with a dispatcher.
Step-by-step explanation:
A security guard who is on a vehicle patrol would most likely use a two-way radio to communicate with a dispatcher. Two-way radios, also known as walkie-talkies, allow for quick and efficient communication between the security guard and the dispatcher.
Unlike other options mentioned, such as a fax machine, alarm system, or cell phone, a two-way radio is designed specifically for instant communication, making it an ideal choice for security guards on the move.
With a two-way radio, the security guard can easily stay in constant contact with the dispatcher, relaying important information, receiving instructions, and requesting assistance if needed.