Applies to: All units
All Focusrite 1/4 inch jack inputs and outputs are mono balanced. Balanced cables have two rings on the end of the connector and are often referred to as TRS (Tip, Ring, Sleeve) cables. Balanced cables are far better at rejecting interference noise than unbalanced cables. This is made possible by the addition of an extra conductor (more information can be found here).
Unbalanced cables (mostly used as instrument cables) have a single ring on the end of the connecter and are also referred to as TS cables (Tip, Sleeve). Unlike Balanced cables, there is only one conductor carrying the signal so interference is not rejected. The 'ground' wire is also not separated inside Unbalanced cables instead it is wrapped around the signal wires as a shield.
When should I use balanced cables?
You should use balanced cables when connecting to/from equipment with balanced inputs/outputs. For example, if you have a pair of speakers with balanced inputs, you should use a pair of balanced cables to connect from the balanced outputs of your interface to the speakers as this will reduce the likelihood of picking up interference noise when compared to using unbalanced cables in the same setup.
Similarly, if you're using a piece of equipment with a balanced output (such as a mixing desk) and you wish to connect that to a balanced input on your interface, you should use a balanced cable.