Newman Atkinson says:

David If you discard your atlas switch motor (save it for something else down the road, and get a tortoise switch motor to operate the switch. The switch motor has 2 extra circuits to do signals and or correctly power the frog if you have a metal frog. The motor has 8 possible wire connections. The 2 on the outside are for the switch motor to run Which will work on various voltages DC. There are 3 pins each 2 circuits in between the two that power the tortoise motor I am feeding the switch itself with 9 volt DC and I run a buss 2 wire cable around the layout to all switches powered this way. One of the 3 wire connections use for your lights. I use 2 dwarf 2 light signal heads one for each direction leaving the switch. A red and a green light for (one for each direction wired together for when it is thrown one way and the other red and green light wired together for when it is thrown the other way That way you will always have a red light on in the direction the switch is not made up for and a green light in the direction the switch is a lined. In addition to the lights on the tracks at the switch you can do and additional set of lights for at the control switch.by doing the same thing while in the same circuit so you will have a red and green light doing the same operation as out by the switch. In othe rwords your monitor by your control switch will indicate the un-aligned direction in red and also alined in green. If done in LEDs the power drain is only slight and they make the LEDs that would fit in your dwarf signal head.

for your lead in track to your switch, most modern signal masts will have a head one above the other where your main line straight will light on the top head and the one for the departure track from the main will light on the next head below. I have not worked out the signal block of the train passing through yet but the signal sent to the mast head for which ever direction you wish to travel would go to the head for that direction and keep the other red. For the lighting I just mentioned above it is simple and will indicate your switch direction both at the tracks and at your control switch and although it may look complicated it really isn’t. Most of these LEDs will work well on 12 volt DC with a resistor in the circuit. Fry Electric for example has LEDs in Red and Green of that size and even yellow, add the resistor in the circuit and you are on your way.
Newman