How are the smoke detectors in aircraft lavatories connected to the flight deck so the crew there can see the warning alarm? Do they have wires all the way from the lavatory to the flight deck, or are they connected in some other way?
A quick Google search suggests the general approach is to minimise wiring by using a data-bus approach to carry information from multiple sources along a minimum number of wires
In earlier analogue avionic systems the number of cables used to transfer information between the various system components was considerable. With these systems, at least one pair of wires has been required for each signal and so a typical installation requires several pairs of wires. With the equivalent digital systems, all the analogue signals are converted into their equivalent and are assigned unique address labels to ensure there are no conflicts. These signals are then transmitted down a single pair of wires, which makes up a data bus. Aircraft data bus systems allow a wide variety of avionics equipment to communicate with one another and exchange data. The type of language used on an aircraft data bus is known as the protocol. There are currently different data bus standards (protocols) that currently account for most of the avionics data interchange on today’s aircraft, and these are: ARINC 429, ARINC 629, MILSTD 1553, MIL-STD 1773, CSDB and ASCB.
I imagine that smoke detectors are just one example of the types of sensor that are integrated into such data-bus systems.
I expect there are several data-bus systems for redundancy and perhaps to isolate different categories of data.
- ARINC 429 as used on A310/A320, A330/A340; 727, 737, 747, 757 767; MD-11 etc.
- ARINC 629 as used on 777
- AFDX as used on A380
- Smoke Detectors interfaced by a safety critical aircraft based CAN-Bus Network