In the government of President Plutarco Elías Calles, this telephone company was acquired by ITT in 1925; on the other hand, it already had a 50-year concession from SCOP for the commercial exploitation of the service. That same year the CTTM obtained the concession to operate national long-distance lines providing service to the capitals of the states of San Luis Potosí, Coahuila, Nuevo León and Tamaulipas. Engineer Eduardo Ortiz, Secretary of Communications, agreed with this company to the necessary cabling between Mexico and the United States for their connection.
The main historical achievement of the CTTM took place on September 29, 1927 at 4:34 p.m., when it made the communication between Mexico and the United States for the first conference held by their respective presidents: General Plutarco Elías Calles and Calvin Coolidge. This great event opened the doors to international long distance service, and two months later the telephone line between Mexico and Canada was inaugurated. Communication with Europe was established until July 1, 1928.