21 TELEPHONE CARRIER APPARATUS COMPRISING CARRIER APPARATUS-NAMELY, CENTRAL OFFICE AND SUBSCRIBER CARRIER UNITS FOR TELEPHONE SYSTEM ADAPTED FOR CONNECTION TO EXISTING CABLE PAIR, BOTH AT THE CENTRAL OFFICE AND SUBSCRIBER'S LOCATION, CREATING AN ADDITIONAL TALKING CIRCUIT OVER THE EXISTING CABLE PAIR TO WHICH AN ADDITIONAL TELEPHONE SET MAY BE SUPPLIED AT A SUBSCRIBER'S TERMINAL, FOR TELEPHONE TRUNK SERVICE (EAS AND TOLL