Crown PZM11
PZM microphone.

This low-cost microphone mounts on a standard wall plate. The PZM-11 resembles a light switch rather than a microphone. Intelligibility is excellent, with low frequencies below the voice range rolled off to reduce the pickup of HVAC rumble. Electronics on the rear of the plate offer screw terminals, eliminating the need for connectors.  Fits into a standard electrical box and is very inexpensive for surveillance or conference room applications.  Powering is via 12-48 volts phantom power.

• Type: Pressure Zone Microphone.
• Element: Electret condenser.
• Frequency response (typical): 80 Hz to 20,000 Hz.
• Polar pattern: Hemispherical.
• Impedance: 225 ohms, balanced.
• Recommended minimum load impedance 1000 ohms.
• Open circuit sensitivity: 5 mV/Pa (–46 dBV/Pa).
• Power sensitivity: –45.5 dBm/Pa
• Equivalent noise level (self-noise): 26 dB SPL typical (0 dB = .0002 dyne/cm2), A-weighted.
• S/N Ratio: 68 dB at 94 dB SPL.
• Maximum SPL: 120 dB SPL produces 3% THD.
• Output connector: Three screw terminals. 1 = ground, 2 = audio hot (in polarity), 3 = audio cold (opposite polarity).
• Polarity: Positive pressure on the diaphragm produces a positive voltage on screw terminal 2 with respect to screw terminal 3.
• Operating voltage: Standard phantom power, 12 to 48 volts DC on screw terminals 2 and 3 with respect to screw terminal 1.
• Current drain: 400 microamperes.
• Materials: Steel plate and high-impact plastic capsule holder.
• Finish: Off-white. May be painted any color; take care to first seal the opening between the mic capsule and boundary plate.
• Net weight: 2.5 oz. (71 g).