The January 4, 1923 WEAF-WNAC broadcast described in this review was the first joint broadcast that used AT&T longlines. However, contrary to the statement in this article, AT&T never built a station in Boston. Instead, in that city, like most others in its expanding radio network, the company contracted with already existing radio stations.
Radio Digest Illustrated, February 3, 1923, pages 1-2:



American  Telephone  and  Telegraph  to  Establish  First  Station  in  Boston--Two  Plants  Send  Same  Program  at  One  Time  During  Tryout

(By  F.  N.  Hollingsworth,  Special  Correspondent)
    NEW  YORK--An experiment in Radiophone broadcasting, the first of its kind ever attempted, has resulted successfully--so successfully, in fact, that the world's greatest telephone corporation is about to launch the establishment of a chain of Radio test laboratories and Radio toll stations that will extend from the Atlantic to the Pacific coasts, both north and south in two lines. This experiment, preparations for which covered several months, was that of simultaneously broadcasting from a New York station on a 400-meter wave length and from a Boston station on a 360-meter wave length. The results are declared by experts to have been flawless.

WEAF-WNAC  Program  Three  Hours  Long
    The New York station was WEAF, of the American Telephone & Telegraph Company at 14 Walker Street, New York city, and the Boston station was WNAC, of the Shepard Stores, on Winter street, Boston. The program was three hours long, and comprised a number of orchestral selections, saxophone and cello solos, contralto and varitone vocalists, and most unusual of all, a bird mimic, whose imitations of bird songs and notes were as clearly and flawlessly heard as though he were in the same room with the listeners.
    From the New York station was run a long distance telephone circuit of approximately 300 miles, equipped at intervals with repeaters or amplifiers and special filters, which equalized the circuits so that the sound came into the Boston station as clearly as it entered at the New York end. To equalize a telephone circuit means that whatever goes into it at one end comes out exactly the same at the other end, or wherever it might be tapped.
    If the lines had not been equalized, the high notes of the saxophone or the low tones of the piano might have been the only ones heard distinctly at the Boston end when broadcast.

Problem  Delicate;  Four  Circuits  Used
    From a technical standpoint, the control of a broadcasting station 300 miles from New York by means of telephone lines is a most delicate problem. Four circuits were used to stage this feat. The first was the "regular" circuit, which carried the broadcast program. The second was an emergency circuit, which could be plugged in should the regular one fail through storm or other interference. The third was a local circuit, used in Boston, for a big side issue program, which will be touched upon later in this article. The fourth was the "order circuit," by which the telephone and Radio engineers in New York and Boston kept in touch with each other and noted progress of the experiment. There were fifteen experts handling the matter at the Boston end.
    Four of these experts were stationed at the Copley-Plaza hotel, about a mile from Station WNAC. Here, in the big ballroom, was installed a "public address system," consisting of four huge loud speaker horns with 50-watt tubes as power amplifiers. A bankers' convention was being held there at the time, and this evening program was rendered to them by combined Radio and telephone as a special entertainment.

100,000  Radiophans  Listen  in
    Owing to the care exercised in adjusting the filters and repeaters, there was no distortion; every note coming over as clear as the original. At least a hundred thousand Radiophans, throughout New England and along the Atlantic seaboard, listened in on this remarkable program. Station WNAC has records of being heard as far south as Porto Rico, and Commerce, Texas, as far east as the Azores, and as far west as Montana. Therefore one can imagine the possibilities of this combined broadcasting.
    The expense of the test was $25,000, but telephone officials say it would have been well worth double that to get the results they obtained.

A. T. & T.  Co.  Plan  First  Link
    Within a very short time it is expected that the American Telephone & Telegraph Company will establish in Boston their own test laboratory and Radio toll station. With the New York station it will constitute the first link in a chain that will be established very soon west, north and south along lines in big cities to the Pacific Coast.
    Nothing definite had been decided until the big test of January 4, but immediately thereafter word came from New York that the Boston station will be established within a few months. The project will not stop in Boston, however, but the chain will be gradually pushed westward. Already hundreds of letters and telegrams have been received at Station WNAC telling of picking up the New York concert, which was duly announced as a simultaneous broadcast, in the usual matter-of-fact way that the Shepard station has. The letters also mentioned the broadcast's remarkable clearness.

What  System  Holds  for  Future
    In time, say experts, the country will be covered with Radio toll stations, so that a big concert in New York, or the inaugural address of a President, or the speech of some silver-tongued orator may be broadcast by contract to any part of the country. Arrangements can then be made for loud speakers installed in some big auditorium where the audience can sit and listen to an evening's program without ever seeing the participants. San Francisco will be able to hear the Metropolitan opera, by contract with the company itself and the telephone company with its Radio toll stations as the intermediary and transmitting agents.
    Political parties can have the greatest campaign orators in the country speak to a hundred audiences simultaneously, at perhaps no more expenditure than would be involved in their traveling expenses, and at a great saving of his time and nervous energy.