There are four possible connections to the LX721: Ground (GND), Common (COM), Positive (POS), Negative (NEG). External devices can be connected to these four nodes via the color coded Banana Jacks. Various subsets of these nodes are also made available on the XLR-F and BNC connectors.

The GND node is the Chassis/Frame/Earth ground. The COM node is the floating/isolated common of the LX721 input circuitry. The POS and NEG nodes are the signal input pair.

The XLR-F connector provides connection to three nodes: GND(1), POS(2), and NEG(3). The BNC connector provides connection to the two signal nodes: POS(TIP) and NEG(SHD).

The LX721 contains a multi-function input capable of providing not only the standard balanced input, but many active power configurations for different types of input devices or transducers. This often eliminates the need for costly external power supplies and preamps. Some examples of possible input mode configurations are shown below.

Eight LED indicators provide status of the various modes and parameters controlling the input. The LED indicators are:
• GND - COM node connected to GND node.
• ACC - AC Coupling in use.
• UND - Under range signal indicator.
• OVR - Over range signal indicator.
• ICP - Unbalanced mode with 4mA Current Source Power.
• PHM - Balanced mode with 48V Phantom Power.
• LVP - Unbalanced mode with Low Voltage Direct Power.
• HVP - Unbalanced mode with High Voltage Direct Power.