Norfolk and Western theme from the Railroad Signals of the US website based on SpDrS60 theme. The following signal masts are supported:-

Prefix	Mast type
	(light) Single head searchlight mast automatic
	(semaphore) Twin head colour position light mast automatic
1_	Single head searchlight mast unified N&W aspect numbers
1a_	Single head searchlight mast standard aspect numbers
1p_	Single head colour position light mast unified N&W aspect numbers
1ps_	Single head colour position light mast standard aspect numbers
1pdls_	Dwarf 'left hand' colour position light with standard aspect numbers
1pdrs_	Dwarf 'right hand' colour position light with standard aspect numbers
1pdr_	Dwarf 'right hand' colour position light with unified N&W aspect numbers
1ds_	Dwarf single head searchlight standard aspect numbers
1d_	Dwarf single head searchlight unified N&W aspect numbers
2d_	Dwarf twin head searchlight unified N&W aspect numbers
2_	Twin head searchlight mast without Lunar aspects unified N&W aspect numbers
2l_	Twin head searchlight mast with Lunar aspects unified N&W aspect numbers
2p_	Twin head colour position light mast with unified N&W aspect numbers
3_	Triple head searchlight mast unified N&W aspect numbers

Automatic aspect numbers
-r	R292	red over red
-y	R285	yellow (over red)
-g	R281	green (over red)
-w	R290	red over yellow
-b	-	unlit


Standard aspect numbers (dwarf rule in brackets)
	main	PL dwf	Sl dwf	aspect
-0	R292	(R292)	(R292)	red
-1	R285 	(R288) 	(R290)	yellow
-2	R281 	(R287)	(R287)	green
-3	- 	(R290)		lunar
-5			(R288)	flashing yellow
-8	-			unlit

Unified N&W aspect numbers
-0	R292	red / red / (red)
-1	-	not used (reserved for R291)
-2	R290	red(s) over yellow (or red used with number plate only)
-3	-	not used (reserved for R289)
-4	R288	yellow / red (searchlight dwarf only)
-5	R287	red / red / green (green / dark searchlight dwarf only)
-6	R286	searchlight only - red / yellow / red or lunar / yellow
-6	R286	Position light only - red / lunar 
-7	R285A	yellow
-8	R285	yellow / (red) / (red)
-9	-	not used (reserved for R284)
-10	R283B	red / flashing yellow / (red) or lunar / red
-11	R283	red / green / (red) or lunar / green
-12	R282A	yellow / yellow / (red)
-13	R282	yellow / green / (red)
-14	R281	green / (red) / (red)
-15	-	unlit


Note that it is not possible to show all aspects on dwarf colour position light heads heads because it requires that the green lamp required for R287 be replaced with a yellow lamp for R288 (left hand) or R290 (right hand). Also some aspects are modified by the presence of number plates so that for example R290 and R292 cannot both be shown on a single head searchlight dwarf. Since it is not possible to include the number plates in the SVG images care must be taken to only use the aspects available for the location and not all that are available in the aspect set.