Designed for paging calls and general announcements, the PM-660 desk-top microphone comes with a large talk switch and a lock lever for easy and convenient operation. Rated Impedance: 600 ?, unbalanced. Rated Sensitivity: -58 dB (1 kHz, 0 dB=1 V/Pa). Frequency Response: 100 Hz - 10 kHz. Output: 2-conductor shielded cable (2.5 m (8.2 ft)) with phone plug. Dimensions: 100 x 215 x 150 mm.