(a) In general. The term “teletypewriter exchange service” means any service where a teletypewriter (or similar device) may be connected, directly or indirectly, to an exchange operated by a person engaged in the business of furnishing communication service, if by means of such connection communication may be established with any other teletypewriter (or similar device). If the teletypewriter or similar device used in conjunction with such service may be connected to such an exchange, the service constitutes teletypewriter exchange service whether or not it is the practice of the subscriber to the service to make such connection, and whether or not the person engaged in the business of furnishing communication service permits the subscriber to make such connection.

(b) Amounts paid. In determining the amount of tax due, the amount paid for the service shall include all charges made in connection with the furnishing of any teletypewriter exchange service, such as salaries of operators, if in the employ of the person furnishing such service, charges for equipment, instruments, and other apparatus. In cases where a person leases lines or channels, equipment, and other facilities used in conjunction with teletypewriter exchange service, the amounts paid by such person for such lines or channels, equipment, and other facilities constitute amounts paid for teletypewriter exchange service, notwithstanding the fact that the lines or channels, equipment, and other facilities used in conjunction with such service are supplied by different persons or in part by the user of such service.

(c) Exemptions. For exemptions from the tax imposed on amounts paid for teletypewriter exchange service, see sections 4253, 4292, 4293, and 4294, and the regulations thereunder contained in this part.