(a) In general. (1) The taxes imposed by section 4251 on amounts paid for wire mileage service and wire and equipment service do not apply to amounts paid for any such services to the extent that the amounts paid are for services utilized by a common carrier, telephone or telegraph company, or television or radio broadcasting station or network in the conduct of its business as such.

(2) The tax imposed by section 4251 on amounts paid for general telephone service does not apply to amounts paid for the use of a continuous telephone or radio telephone line or channel to the extent that the amounts paid are for use by a common carrier, telephone or telegraph company, or television or radio broadcasting station or network in the conduct of its business as such, if such line or channel connects stations between any two of which there would otherwise be a toll charge. A line or channel connects stations between which there would otherwise be a toll charge if the telephone company makes a toll charge for a single message transmitted between the two stations in the case of the ordinary residential and business or commercial telephone service. A line or channel connecting two stations is considered a continuous line or channel if such line or channel does not connect with any switchboard interposed between the two stations, which makes it possible to carry on two or more independent conversations simultaneously. Where a line or channel connects with such a switchboard, the exemption is inapplicable to so much of the amount paid as is attributable to the portion of the line or channel which extends from a station to a switchboard located in the same local service area.

(b) Exemption inapplicable. This particular exemption is not applicable in the case of the taxes imposed on amounts paid for other services by section 4251, even though such services are utilized by the companies described in the conduct of their business as such.