Radio age research, manufacturing, communications, broadcasting, television (1941)

tion headquarters; provide radio telephone and teletype communications between the project and executive offices in Caracas, 270 miles away; permit conversation over a 206-mile triangle linking the mine and railhead at Cerro Bolivar with head offices at Ciudad Bolivar and the newly constructed port of Puerto Ordaz at the mouth of the Caroni River, and help to control traffic on the 90-mile single-track railroad from the mine to the port through remote operation of signals and switches. Rail Traffic Control Like the Cerro Bolivar project itself, the remote control system which handles two-way traffic on the single line railroad is itself a revolutionary development. The use of a microwave channel in conjunction with a railroad signal system was first tested in 1946 by RCA, Union Switch & Signal (a division of Westinghouse Air- brake Co.), Western Union and the Pennsylvania Rail- road over a 900 mile circuit linking Washington, Phila- delphia, New York and Pittsburgh. On the Venezuela project, the system developed through these tests has been put to regular use for the first time. The system utilizes RCA facilities installed to handle telephone and teletype communications as well as the radio waves controlling signals and switches at the four sidings along the railroad. Radio towers capable of carrying the microwave channel and transmitting and receiving VHF-FM have been located at both Cerro Bolivar and Puerto Ordaz, and each of the locations is equipped with two transmitters, two receivers, two trans- mitting aerials and two receiving aerials. The two sidings nearest the port are governed by waves transmitted from the Puerto Ordaz tower, while the two nearest the mine are controlled by waves sent over the microwave channel from the port to Cerro Bolivar tower. The transmitting and receiving facilities, together with centralized traffic control and coded carrier systems developed by United Switch & Signal, enable a single operator at the port to regulate all rail traffic in both directions simultaneously. Components of System To weave the communications network serving the far-flung operation, RCA has provided some 50 trans- mitters and receivers for installation at fixed points, on dredges, tugs and other vessels, in construction crew barracks and project offices, aboard trains, and with surveying parties. The entire collection breaks down into these separate systems: (1) A triangular radio-telephone circuit comprising a duplex (two-way) microwave system connecting with regular telephone switchboards at the mine, the port and Ciudad Bolivar. Included in the system is an auto- Radio networks link all principal points involved in the Venezuela operations of the Orinoco Mining Company. matic repeater station located on a rise at Piacoa, at the head of the Orinoco delta, for communication between Puerto Ordaz and dredges which keep clear a 176-mile deep-water channel for ore vessels from the port out to the open sea off the coast of Trinidad. (2) A high-frequency radio system connecting the project offices at Ciudad Bolivar with the executive offices of the Orinoco Mining Company in Caracas, 270 miles to the northwest. This system provides a duplex telephone channel and a teletype circuit working on frequency-shift keying. The high frequency transmitter at the Caracas end could not be located within the city proper and was placed instead at Petare, about 10 miles east. A VHF link from the Caracas office to the trans- mitter provides full remote control of the transmitter and handles the outgoing traffic. (3) Mobile facilities to provide communication between construction camps, vehicles, surveying parties and other units likely to be on the move, and to permit communication between front and rear of trains or between train and dispatcher. From the start, RCA facilities have been used to en- sure rapid progress. The principal paths for the radio circuits were surveyed in 1950, when certain temporary channels were installed for the beginning of operations by the Orinoco Mining Company. The relatively long, distances to be covered over barren territory required special care in site selection and the use of special an- tenna to avoid the need for repeater stations at inter- mediate points. The system was engineered and installed by the RCA International Division with an auxiliary field staff" from the RCA Service Company. The engineering project in New York was directed by D. H. Pain with field engi- neering originally under the direction of G. G. Gerlach, later under L. A. Shotliff. Supervising all of the radio installations for the Orinoco Mining Company was Henry Carroll, communications superintendent. Paul F. Godley is consulting engineer. 22 RADIO AGE