Federal Signal's Model SLM500 is a multifunctional LED beacon and sounder combination developed with a multiple input technology that allows three separate levels of alarm (alert, pre-alarm, alarm) controllable via independent electric contacts. Channel 1 includes a simulated strobe (triple flash) visual signal only. Channel 2 adds an audible tone, selectable from 32 tones via dip switch, to the simulated strobe effect. Channel 3 includes a steady light and a second, unique tone selectable from 32 different tones, for a total of 64 unique tones. The volume of a selected tone is adjustable from 65dBa-105dBa at 1M for the highest performing tone. Its enclosure is made from a self-extinguishing polycarbonate material with high impact and UV resistance. To complete your signal, a Federal Signal StreamLine Modular Base SLMBD, SLMBP, SLMBS, SLMBT or SLMBW is required.