(a) In general. Except as provided in paragraph (b) of this section, the tax imposed on amounts paid for general telephone service is not applicable to a single telephone conversation paid for by inserting coins in a public coin-operated telephone. The tax imposed on amounts paid for toll telephone service or telegraph service is not applicable to a single telephone conversation for which a tool charge is made (see paragraph (a) of §49.4252-2), or to a telegraph message, if the charge for such toll telephone service (including any additional charge for overtime) or telegraph service is less than 25 cents and is paid for by inserting coins in a public coin-operated telephone.

(b) Exception where service furnished for a guaranteed amount. Where a coin-operated telephone service is furnished for a guaranteed amount, the amount paid under such guarantee plus any fixed monthly or other periodic charge is subject to the tax imposed on amounts paid for general telephone service. The tax applies to the full amount of the guarantee whether such amount is paid out of receipts from the coin-box of the telephone or from funds of the subscriber.