Complex sentence: An active pulsing red or white light is seen when well above or well below which allows the pilot to determine his position within the signal format and to determine what corrective action is needed to return to the proper descent profile.
Split into simpler sentences: An active pulsing white light is seen when well above or pulsing red when well below. This allows the pilot to determine his position within the signal format and to determine what corrective action is needed to return to the proper descent profile.