The AV-DC4 is a mono transformer-coupled audio divider/ combiner module for use with balanced, low or high impedance audio inputs and outputs. Input and output connections are provided on XLR jacks with gold-plated contacts. The AV-DC4 features four identical channels. Each channel may be used as either an input or as an output. Two XLR jacks are provided on each channel. The female jack is used if the channel is being used as an input; the male jack is used if the channel is being used as an output. The shield (pin 1) connections of both XLR jacks on a particular channel are normally connected to ground. The GND LIFT switch on each channel is used to disconnect the shield from circuit ground at audio frequencies.Galvanic isolation between each of the channels is provided by a studio quality audio transformer. The AV-DC4 breaks the "ground loop" connection that can produce hum in a sound system. The input connector shield does provide a radio frequency ground return, thereby preserving system immunity to radio interference.The four channels allow multiple uses for the AV-DC4. A single mono audio source can be divided to feed one, two or three mono equipment inputs. A stereo source can be combined to mono, feeding one or two mono equipment inputs. A mono source can be divided to feed a stereo equipment input (left and right). A stereo source can be combined to mono and simultaneously be divided to feed the mono signal to both the left and right inputs of stereo equipment. Ground lift may be selected individually on any of the channels.The AV-DC4 is a rugged product designed for portable use. For fixed installations, a mounting bracket is included.