(a) In general. The tax imposed by section 4251 on amounts paid for general telephone service does not apply to amounts paid for any such service furnished on or after January 1, 1963, to the extent that the amounts paid are for use of any telephone or radio telephone line or channel (including equipment, instruments, and other apparatus furnished exclusively for use in connection with the line or channel) in the conduct of a trade or business when such line or channel is furnished between specified locations in different States or between specified locations in different counties, municipalities, or similar political subdivisions of a State. The term “trade or business” as used in this section includes activities of organizations which are conducted with no purpose of gain or profit. A line or channel is considered to be furnished between specified locations only when the line or channel connects preselected points without the use of switching functions performed by a communications company exchange. Where an amount is paid which includes a charge for such a line or channel and also a charge for the service provided by means of switching functions performed by a communications company exchange, the exemption is applicable only to that portion of the amount so paid as is attributable to such a line or channel. The preselected points must be located in different States or in different counties or municipalities of the same State. If the preselected points are located in a State in which the political subdivisions are not denominated as counties or municipalities, then the preselected points must be in different political subdivisions of such State which correspond to counties or municipalities. For purposes of this paragraph the term “municipality” means the largest political subdivision of a State below the level of county or similar subdivision. For the exemption to apply, the charge for the service must be billed in writing to the person paying for the service and such person must certify in writing that the service is for use in the conduct of a trade or business.

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