Until the 1970s, the Bell System (AT&T) supplied all equipment related to residential and commercial telephone services. In those rare instances that businesses needed to interface their own equipment (CPE) to the PSTN, Bell required that equipment to be isolated via a protective couplers, installed and maintained by Bell and paid for by the customer.
Created 2023-03-09 06:31 by Stephen B (Revised 2023-03-10 04:19)