The Model 515BSM is a low-impedance, dynamic microphone designed for hand-held or fixed use. Designed for hand-held or fixed use. The unidirectional (cardioid) pickup pattern provides excellent reproduction of voice and effective rejection of feedback. The microphones are supplied with a push-to-talk switch and a four-conductor, retractable cable (2 shielded conductor). These microphones are especially suitable for use in paging systems, public speaking, stage performance, and public address systems. They are also highly recommended for other applications requiring both hand-held and fixed installation operations. The microphones are wired with the microphone circuit normally open for use in parallel microphone installations.