The Microtech Gefell UM 900 is the first switchable pattern, valve condenser microphone which can be connected to industry standard 48 volt phantom powering using a normal 3-pin XLR microphone cable. This is made possible by an advanced circuit design for the amplifier and internal power supply. The pickup capsule uses a traditional, proven design with two large, gold plated plastic membranes.

Three switches are located around the body of the UM 900. The switch in the front selects the polar pattern: omni, wide cardioid, cardioid, hyper-cardioid and figure 8. Located 120 degrees to each side are switches for gain adjustment and low frequency roll-off.

The unusual shape of the microphone's body is especially designed to minimize undesirable reflections of sound toward the pickup element.

Acoustic influences which could result from the housing resonance and/or mechanical vibration are reduced by the robust construction and by a special fixture within the microphone's housing which dampens vibration.