Shure 545SD-LC Microphone dynamic, with switch

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. 

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

Type:  Dynamic
Frequency Response: 50 to 15,000 Hz
Polar Pattern: Cardioid (unidirectional)--uniform with frequency, symmetrical about axis
lmpedance: Dual. Microphone rating impedance is 150 ohms (250 ohms actual) for connection to microphone inputs rated at 19 to 300 ohms and "High" for connection to high-impedance microphone inputs. Wired for low impedance as supplied.
Output Level: LOW @ 1,000 Hz: Open Circuit Voltage* -58.0 dB (1.3 mV); HIGH @ 1,000 Hz: Open Circuit Voltage* -35.0 dB (17.6 mV) *0 dB = 1 volt per Pascal (1 Pa = 94 dB SPL)