The phrase "call arm" refers to a tool or device used to signal others. Synonyms for this phrase include "signal arm," "beckoning arm," "summoning arm," and "gesture arm." Each of these phrases describes an arm-like tool that is used to communicate a message or to beckon another person. The use of a "call arm" or any of its synonyms is especially common in large public spaces such as airports, hospitals, or concert venues. By using these tools, individuals can quickly and easily communicate with others without the need for shouting or yelling.