3) Advance Starter:
It is a stop signal provided ahead of the starter signal, and therefore it is the last stop signal on departing station limits.
C) Permissive Signals
A permissive signal doesn’t have a stop aspect and is used to give the driver an idea of the position of a stop signal which is coming up ahead. A permissive signal also has a “P” marker plate mounted on its pole to give the driver the indication that it’s a permissive signal. This is necessary because in case a signal is totally blank due to a technical fault a Stop Signal cannot be passed by the driver and he must stop at the signal and await further instructions but if a permissive signal is found to be blank, it may be passed at a restricted speed and the concerned station master may be informed of the failure. A permissive signal is also called a Distant Signal.
ON and OFF aspects: A signal which is displaying its most restrictive aspect is termed as being ON. For example a stop signal displaying the red aspect is termed to be ON. But a permissive signal displaying the yellow aspect is also ON because yellow is its most restrictive aspect.