View larger View larger Shure 545SD-LC Cardioid Dynamic High or Low Z On-Off Switch Classic Unidyne instrument mic features selectable dual-impedance operation with a silent on/off switch. Description The Model 545SD is a dual-impedance, unidirectional, dynamic microphone. Shipped connected for low-impedance operation, it features a silent magnetic reed on/off switch. The Classic Unidyne is a favorite for instrument pickup and recording,and can be used on lecterns for public address systems such as those used in political conventions and legislatures, convention halls, hotels, public auditoriums, stadiums, schools, and churches. Product Details The predecessor to the SM57, the 545SD Classic Unidyne Instrument Microphone is a dual-impedance, unidirectional, dynamic microphone. Shipped connected for low-impedance operation, the 545SD features a silent magnetic reed on/off switch with lock-on option. A favorite for instrument pickup and recording, the 545SD can also be used on lecterns in public address systems. Features: Optimized performance in voice processing and computer voice recognition applications.Smooth frequency response with excellent fidelity in the voice range.Cardioid pickup pattern and close-talking operation keep unwanted signals and background noise at low levels.Constant output over voice spectrum when close talked.Humbucking coil minimizes undesirable hum effects such as CRT interference.Low-impedance design permits long cable runs in extreme hum fields.Small unobtrusive design does not interfere with CRT visibility.Rugged and reliable for years of consistent operation.