Development of the Rio de Janeiro automatic telephone network

Since 1930 the number of telephones of Rio de Janeiro has risen from 2.9 per hundred of the population to 4.8. At that time there were seven manual exchanges; by 1939 conversion will be complete to automatic working using rotary equipment manufactured at Antwerp. Air-conditioning was justified on the score of expense by special local conditions in two exchanges, but the remaining apparatus will have semitropical finish, only dust being removed from the ventilating air. With a few exceptions all buildings are equipped to house two 10000-line units, the total capacity being 160,000 lines, with easy extension. The supply is floated across batteries, shunt generators and mercury-arc rectifiers being used; in the future selenium rectifiers will also be used. Special intercepting and meter monitoring facilities are provided, in view of the high turnover of lines and exchange changes. About 50 operators are engaged at a centralised information board. The testing and trunk facilities are also described, together with illustrations of the plant.