I am replacing a light switch with one including a neon indicator. There is only one cable to the switch but the new switch has live and neutral terminals for both 'in' and 'out'. Which terminals do I use?
You use Live In (supply) and Live Out (load).
The neon will not work, unless you also have a neutral present at the switch.
You'll need to call an electrician to change the cable between lamp and switch.
In this installation, power comes into the lamp, rather than the switch. There's nothing wrong with that, but the wiring in this house is older and does not conform to NEC 2011. As such, there is no neutral (return) wire in the switch box.
Without a neutral wire, it is not easy to power anything in the switch box that needs power. Normal switches do not.
What your switch actually has is
- For the switch: line (always-hot) and load (switched-hot).
- For the indicator: supply (switched-hot) and neutral.
On some switches, two of those terminals are wired to be common, but can be separated.
If you want the pilot on when the switch is off, there's a chance of doing this without rewiring. Check your switch and lamp to see if it supports this, but the pilot can be wired to be in series with the lamp., so it lights when the switch is off.