Overview
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 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
Exceptionally uniform cardioid pattern minimizes feedback
Selectable dual-impedance operation
Silent magnetic reed on/off switch with lock option