9.02. Duties of Loco Pilot and Guard when an Automatic Stop signal on
double line is to be passed at ‘on’.––
(1) when a Loco Pilot finds an Automatic Stop signal with an `A`
maker at `on`, he shall bring his train to a stop in the rear of the
signal....
more...

After bringing his train to a stop in the rear of the signal, the
Loco Pilot shall wait there for one minute by day and two minutes
by night. If after waiting for this period, the signal continues to
remain at `on`, he shall give the prescribed code of whistle and
exchange signals with the Guard and then proceed ahead, as far as
the line is clear, towards the next Stop signal in advance exercising
great caution so as to stop short of any obstruction
source: click here
there was video explaining this too, but I'm unable to find it.
This is General rule, every zone has the power to make some changes to it (that comes under subsidiary rule)
The subsidiary rule for CR states this, once you cross the red signal:
S.R. 9.02-5. Distance between two trains in Automatic Signalling territories after passing an Automatic Signal at ‘ON’ -
(a) After passing an Automatic Stop signal at ‘ON’ the Driver of the train hauled by any locomotive shall ensure that minimum distance of 150 metres or two clear OHE spans is maintained between his train and the preceding train if any or any obstruction on the line ahead. However, in the case of EMU train the minimum distance of 75 metres or one clear OHE span shall be maintained between EMU train and a preceding train if any or any obstruction on line ahead.
(b) In special circumstances like flood etc., or if necessary to assist a disabled EMU train the following EMU train may be drawn closer to the preceding EMU train, exercising great caution
source: click here
rules are pretty dense actually, kudos to the LP's who remember all this, and the guards/LI's who help enforce it.