100. In the interpretation of these rules, any word, term, or phrase used herein shall be taken to mean:1. AREA OUTSIDE OF BASE RATE AREA - That area within the exchange service area which does not have continuous development and lies beyond the base rate area. Generally, rural multi-party service is furnished within this area. However, primary service may be furnished at base rate plus a charge based on mileage or zone differentials.2. BASE RATE AREA - A continuous, closely built-up section of the exchange area in which the base rate applies without mileage charge.3. CARRIER CIRCUITS - A circuit provided by the use of electronic carrier equipment whereby more than one conversation can be transmitted over one metallic circuit or radio path at the same time.4. CENTRAL OFFICE - The inside equipment of the telephone company as an operating unit, where connections are made between subscriber's lines and trunk and toll lines.5. COMMUTED MILEAGE AREA OR LOCALITY RATE AREA - A definite area outside the base rate area where service is furnished at base rates plus additional charge based on a uniform mileage measurement.6. EXCHANGE - The telephone company system providing service within exchange service area.7. EXCHANGE AREA - An area in which is located a telephone central office or offices within which area the telephone company holds itself to provide service.8. EXTENDED AREA SERVICE - The type of telephone service that furnishes toll free local service between closely situated exchanges having a common community of interest.9. EXTENSION OF SERVICE - Extension of existing facilities to serve a customer, customers or a new area not presently served.10. FOREIGN CENTRAL OFFICE SERVICE - Exchange service furnished by means of a circuit connecting a customer's telephone with a central office of the same exchange but outside of the central office district in which the telephone is located.11. FOREIGN EXCHANGE SERVICE - Exchange service furnished by means of a circuit connecting a customer's telephone with a central office outside of the exchange area in which the telephone is located.12. GROUND RETURN CIRCUITS - That type of circuit that utilizes, in place of one of the two wires required for a metallic circuit, the ground as a returned circuit.13. JOINT USER - The person, firm or corporation who shares a customer's service under a specific contract and in accordance with tariff provisions, but 17 would not otherwise be entitled to such joint use.14. METALLIC CIRCUITS - That type of circuit that utilizes more than one wire.15. OUTSIDE PLANT - The telephone company equipment installed on, along, or under streets, alleys, highways, or on private rights-of-way between the central office and subscribers' locations, or between central offices.16. PRIMARY SERVICE - Generally considered to be 1, 2, or 4-party service.17. RURAL SERVICE AREA - That area within the exchange service area which is sparsely developed and lies outside the base rate area. See definition for "Outside Base Rate Area."18. SERVICE CONNECTION CHARGE - A charge made to a customer for the purpose of reimbursing or partially reimbursing the telephone company for the cost involved in connecting telephone facilities upon customer's premises.19. SERVICE LINES - Those lines which are owned and maintained by the subscriber.20. STATION - The telephone instruments and associated equipment installed for the use of a subscriber on his premises.21. SUBSCRIBER - Same as "customer".22. SWITCHING SERVICE - That service performed when calls are switched from a service line to another line terminated in the company's board.23. TELEPHONE COMPANY - Any person, firm, partnership, or corporation engaged in furnishing telephone service to the public under the jurisdiction of the Public Service Commission. Each telephone company shall file with the Commission regulations enumerating and comprehensively defining the classification of service available to subscribers in its exchange or exchanges.