Which type of radio is NOT commonly used by security officers?

The choice of "landline radio" is not commonly used by security officers because it is not a standard term or type of equipment found in typical security communication setups. Radios used by security personnel usually fall into specific categories: base stations, which are stationary and serve as a central communication hub; mobile radios, which are installed in vehicles for on-the-go communication; and portable radios, which are handheld and used by security officers for ease of movement during their patrols and duties.

In contrast, a "landline radio" suggests a wired communication system rather than a radio frequency-based system, which would not meet the operational needs of security personnel who rely on immediate and flexible communication in various environments. This distinction highlights why the other options are preferred and regularly utilized in the field.