A small-sized, lightweight portable telephone has a microphone mounted on a rotatable arm that can be released into a use position using only one hand, which is also grasping the telephone. Even if an excessive load is applied to the microphone arm, which is rotatably supported relative to the telephone main member, damage is prevented by a spring-loaded detent mechanism. The microphone arm has built in it a core member formed of a shape-memory alloy and constituted by a flexible casing, so that deformation can occur without permanent damage to the arm.