Part 1: This is a throwback to when alarms went out over the bells. "5" was the preliminary signal for an engine company, "7" for a truck. So if you wanted to special call, say, engine 15 to box 1234 you would send out "5-1234-15"; then ladder 2 to the same box as "7-1234-2". Individual s/c's did not go over the radio.
But if there was an incident requiring just 1+1 to respond to that box, the dispatcher would "tip" the 1st due engine & truck by telephone, and then transmit 57-1234 over the bells. Traditionally 57 signals were, and apparently still are, given out over the radio just like pulled boxes & phone alarms.
I hope my memory servces correctly, but the bell signals as they were back when were......
2: 12 noon time signal (not given in combination with anything else)
3: special building box (a/k/a class-3) preliminary [it preceded the box & terminal numbers, as in 3-1234-1]
4: battalion preliminary
5: engine preliminary
6: Marine Co. preliminary
7: truck preliminary
8: squad preliminary
9: Misc special unit preliminary (depending on terminal. e.g. Ambulance 2 was 9-xxxx-2, Thawing apparatus was 9-xxxx-64").
10: rescue preliminary
11: telegraph test signal
13-1-13 air raid drill
13-2-13 the real thing
15: engine relocation
17: truck relocation
65-2: monitor radio for announcement
5-5-5-5: monitor radio for LOD death announcement
"Signal 18" and "Signal 9-2" could be tapped in from a telegraph key contained inside every street box. An aracane telegraph signal that most people never heard of was 2-9, which meant "return the Marine Company".
Part 2: I really dunno, but the rig posted in this thread looks like a dpeartment maintenance vehcile of some sort.
