The LS 10 and LS 10A Loudspeaker Line Selectors allow switching between two sources in a Public Address system broadcast, for example between background music and general paging. Utilising an array of relays, the units each have 10 switches on the facial for manual control of the selection for 10 individual zones. The LS 10A however comes with an additional ALL CALL button, which automatically selects all the 10 zones on the unit. The ALL CALL control on the LS 10A unit can be cascaded to other LS 10 units to simultaneously activate all zones of units connected it.

Apart from manual zone selection, the LS 10 and LS 10A can also be remote controlled via a 15-pin D-Type parallel connector input at the rear of the unit. With an optional Remote Override signal, the front panel settings can be temporarily overridden while a new set of remote controlled zone selection takes precedence.