Question:
I am interested in obtaining more fire alarm cable for an existing installation that Holmes Security had installed back in the 1980s. I am trying to relocate the wire across a kitchen, and thus need to find the exact cable (or at least the impedance of the wire) so I can run it another 40'. The wire has no markings, but the spool that it came from had the following markings: 1608 2/18 6/22 It is an 8 conductor cable with 2 conductors being 18 awg and 6 conductors being 22 awg. The colors of the 18 awg conductors are black and red (16 strands each that have a silver color). The other conductors have the following colors: white, orange, green, blue, yellow, and brown (7 strands each that have a silver color). All wires are stranded, unshielded, and located in a grey (PVC?) jacket. All conductors are not twisted pair. Could you tell me what type of cable this is? Was this a common fire alarm cable? Do you know where I could get a small amount of this cable (say 50') or could you tell me what would be a good substitute to match the impedance of at least the 22 awg cable- the 18 awg is power, so I'm not too concerned about matching that.

Answer: Sounds to me that the company that installed this may have used this cable for other devices on your system. Can you tell us what kind of detectors are being powered by this 18 AWG wire, and which other wires are in use? Are you extending the cable from the last device on the system? What kind of system is it? Where are the end-of-line resistors located for the circuit(s) you will be interrupting? You may well be able to source the cable you require from any number of electronic cable suppliers (check your local yellow pages), but if you're doing work on an engineered fire system, you may have some additional requirements to meet as well. You should check your local jurisdiction if this is the case.