Hi David,
All N unless specified otherwise.
Arnold (colour light only) A7602, 03, 04, 10, 22, 23.
Fleischmann 9200, 01, 05, 06, 9220, 9225
Minitrix 66748, 66758, 66759, 66760, 66763, 66766
Roco 20010 (N), 40020, 40021 (HO)
Marklin of course HO & N
Trix HO nop details.
If you need more detial, let me know and I can send images or definitions.
Of course, unlike track, signals are common across all manufacturers so a single symbol, appropriately scaled, could be used for all makes (unless you are planning on showing the physical size of the base unit. Symbols could be the standard ones used on prototype trackplans as in
http://www.sh1.org/eisenbahn/rsym.htm.
Best wishes,
Chris.