Shure 565SD-LC Microphone without Cable, Silent Magnetic Reed On/Off Switch with Lock-on Option Versatile, high-quality microphone with sound characteristics similar to the SM58 Selectable dual-impedance operation; 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. Silent magnetic reed on/off switch with lock-on option Polar Pattern: cardioid (unidirectional)--uniform with frequency, symmetrical about axis 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)