Simplex 4905-9903 — red adapter plate that mounts a TrueAlert speaker/strobe on a Simplex 2975-9145 back box.
The 2975-9145 is a red Simplex mounting box measuring 7 7/8 in. H × 5 1/8 in. W × 2 3/4 in. D. Its opening does not match a TrueAlert appliance, so on a retrofit this plate bridges the two: it closes off the old box and presents the mounting the appliance expects, in either orientation. Simplex lists the 4905-9903 specifically against S/V appliances — speaker visible, the speaker/strobe devices — and that is what separates it from the other plates fitting the same box.
- Adapts a Simplex 2975-9145 box to a TrueAlert S/V wall mount appliance or a rectangular S/V
- Mounts vertically or horizontally
- Red finish, to match the box
- Retrofit accessory; the plate only, with appliance and box ordered separately
On the same 2975-9145 box, 4905-9931 is the plate for a TrueAlert horn, V/O or A/V, not for a speaker/strobe. 4905-9836 and 4905-9839 are cosmetic plates for a flush 4 in. square box, and 4905-9946 and 4905-9947 are the deep surface mount skirts for an S/V.
