Radio Monitoring and Interference Control
73. As in previous years, the greatest single interference source affecting telecommunication services, particularly VHF radiotelephone circuits, was plastic-welding machines. Investigations into complaints arising from interference of this nature necessitated 330 visits being made to industrial premises where 164 unlicensed machines were found in 55 different workplaces. On several occasions faulty machines were sealed in order to prevent continued disruption of essential communications.
74. Five prototype plastic-processing machines employing radio fre- quency generators submitted by manufacturers, or their agents, for type-testing were subsequently approved for local use.
75. The operating parameters of civil aviation beacons and ground/ air systems were checked at regular intervals. The frequencies of 1,437 mobile radio system transmitters were measured to ensure that they were operating within prescribed tolerances. This represents an increase of almost 100% over the amount of similar work done during the preceding year. The transmitters of 187 ships undergoing radio survey were also checked.
76. Supervisory monitoring of local radio communications was continued, and proposed new channels were examined prior to allocation.
Government Telephone Services
77. The Department plans and makes arrangements for the provision of telephone services for other Departments. The number of Government telephone facilities in operation at 31st March, 1972 is listed below:
Direct Exchange Lines and Junctions Official Residential Telephones
Extensions
***
Private Wires, Tie Lines and Long Line Extensions
Switchboard Extensions
Intercom. Units
Total
***
**
***
*
4,824
1,233
1,986
409
6,367
1,311
16,130
78. Five new Private Automatic Branch Exchanges and four Private Automatic Exchanges were planned and completed during the year. A further 14 P.A.B.X.s are currently in the planning stage, including a very large system for the Royal Hong Kong Police. Three other major projects involving both telephone and radio services are in hand for the
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