BS680FC (BS680F With Ceramic Connection) Fire Proof EN54Constructed with metal cabinet, the speaker is ideal for use in a voice alarm system. Can be surface or flush mounted to the wall. Either concealed in wall wiring or exposed wiring can be used for speaker cable connection. The speaker structure of direct wall mounting with screws prevents the speaker from falling easily even if an outward force is applied to. The input impedance can be easily changed by changing the tap position of the transformer.