Check this thread:
https://ogrforum.com/t...35#69285198791014535
The "low-voltage" 12V DC automotive market may be the largest application for illuminated switches. While these automotive switches handle AC voltages, some consideration is required for the illumination since most/all use LEDs which don't take kindly to AC voltages. The thread and the earlier referenced thread therein also shows a quirk about these illuminated automotive switches that makes them best used in conjunction with 12V DC relays to perform the actual switching of the AC power to blocks. While it seems complicated, it is not expensive considering handsome/attractive 12V DC LED-illuminated switches are less than $1...and 12V DC relays are also less than $1.
You can find illuminated switches with built-in LEDs which are electrically separate from the switching function. In other words, the LED is simply two terminals on the switch body. You wire up the LED to whatever you want which may have nothing to do with what the switch is doing. These will cost several times that of an automotive switches with far fewer options/styles. The advantage of this method is you can choose to power the built-in LED from two "feedback" wires from the block itself showing track voltage is actually present. Obviously an illuminated switch powered by the switched voltage only shows the voltage at the switch...not what is actually at the controlled block.
Here's an example I found from DigiKey from the NKK M2100 LED-illuminated switch family. The datasheet goes through the various options which can be overwhelming. $7.45 qty 1. And you must provide the external components to convert your 20V AC voltage to the few Volts DC to drive the LED.
While the relay method may seem like more wiring, note that the high-current can be switched closer to the point of use. If you draw a wiring diagram with dimensions of wire-run lengths, you may find the relay method is actually simpler. This is because the control wires running from toggles to relays (relays placed closer to blocks) can use low-current wiring (e.g., multi-conductor phone cable). Otherwise you must run high-current bulky wires (e.g., #14/16 cable) all the way from the control panel toggles to blocks.
Another consideration is the easy of mounting the switch. I notice many of the automotive illuminated switches require a large mounting hole (e.g., 3/4"). This may require special tools/bits you may not have especially if cutting acrylic, Lexan, or whatever. For example, it may be simpler to make two ~1/4" holes than one 3/4" hole. In other words, use a standard mini-toggle ($1-2) with a ~1/4" mounting hole and a separate standard 3mm or 5mm LED (10 cents) with an LED mounting clip/bezel (10 cents) to give that finished-look.
