Complex sentence: Weigman was on a party line when he held the star button and voice on the other end replied "Moderator On" and as he pressed the pound key, he gained access to the numbers of all the callers on the party line.
Split into simpler sentences: Weigman was on a party line when he held the star button and the voice on the other end replied "Moderator On". As he pressed the pound key, he gained access to the numbers of all the callers on the party line.