Complex sentence: Up until the 1970's, New Zealand's telephone network consisted primarily of step by step telephone exchanges, local telephone number lengths varied from 3 to 6 digits depending on the size of exchange and population of the local calling area.
Split into simpler sentences: Up until the 1970's, New Zealand's telephone network consisted primarily of step by step telephone exchanges. Local telephone number lengths varied from 3 to 6 digits depending on the size of exchange and population of the local calling area.