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In small unattended outside plant telephone equipment buildings, considerable energy may be expended to operate the air conditioner and/or heater that prevents indoor temperature and relative humidity from exceeding specified limits. An important factor in determining how much energy is used is the amount of insulation in the walls and roof. At high internal heat loads (≫20 W/ft2), which are fairly...
A calculation model for heat transfer by natural convection from vertical parallel plates with chimney is presented. Results from applications on circuit boards as well as a plate fin cooler are presented. The model is also used for calculations on the circutation from the circuit boards to the cooler.
This paper describes the use of grourndwater to cool telephone exchanges and highlights some of the practical problems which have to be solved when designing this type of cooling installation. An indication of the financial savings is given as well as situaticns in which groundwater cooling techniques could prove beneficial.
Solid state, i.e. digital telecommunications systems, use computer technologies, and require computer grade, highly reliable environments for long life and optimum reliability. This paper addresses the requirements, selection, and major characteristics of close control, packaged air conditioning systems, developed specifically for computer and telecommunications environments. Presentation material...
The air-conditioning of telecommunication centers is generally characterized by an all year high cooling load and by low outside air requirements. Therefore a chance would exist for the inexpensive so-called "free cooling" by use of colder outside air during most of the operating time throughout the year, if the expenditure for the then necessary humidification would not soon exceed the...
Natural convection cooling is widely used for temperature control in electronic equipment. The amount of heat that can be removed is determined by three factors: the temperature difference, the cooling area and the heat transfer coefficient. Heat transfer calculations for idealized cases are relatively easy and the results of these often give a good lead for the mechanical design of electronic equipment...
When the compressor of a packaged air-conditioner for cooling a containerized station stops operating, the relative humidity of the room exceeds the upper limit of the specified range. The high relative humidity phenomenon is caused by water forming on the cooling coil of the air-conditioner. This water condenses, while the compressor is running, and is vaporized by the fan airflow which continuously...
The number of telecom switching offices in the Swedish network is about 7000 and among those, roughly 90% have 2000 lines or less. When converting the telecom equipment from electromechanical to SPC technique, the number of minor switching exchange offices will increase. This paper describes two power supply systems introduced by the Swedish telecom administration as standards for minor telecom installations...
This paper describes a DC power supply consisting of a number of parallel operating charging rectifier units operating on a common battery bank. This system is developed for and in cooperation with The Norwegian Telecommunications Administration. A control system takes care of the load sharing independant of the number of charging rectifier units in parallel. A monitoring system can take care of units...
A complete 24 VDC, 50 A power plant for telecommunication applications is described which fits in 10?? inches (6 rack positions) in a 19 inch relay rack. Among the meter, alarm and control functions provided are a switch selectable digital meter to monitor battery and load voltage and current, a low voltage disconnect control, and a battery charging control to protect the gel cell batteries. Up to...
Programmable logic control (PLC) microprocessors are designed to take the place of hard-wired relay and contactor-control assemblies. Among the multiple advantages offereo are a wider scope of task adaptation and protective devices, rapid functional testing with less instrumentation in a small space: and greater reliability and endurance following therefrom. These merits can of course be put tc good...
A power-feeding system developed for digital signal-transmission systems on optical fibers is presented. It consists of 1 to 3 power-feeding units (400 mA, 700 V each), a power-feeding control unit, the power-feeding cable and the remotely-fed converters to supply the loads. The power-feeding control unit performs a route test before the power-feeding is switched on, locates route faults and monitors...
KOKUSAI DENSHIN DENWA CO., LTD. (KDD) will construct the transpacific optical fiber submarine cable system (TPC-3) between Japan, Guam and Hawaii in 1988, with AT&T. This system has a total system length of about 9000km. The power feed equipment (PFE), for long haul optical submarine cable system like as TPC-3, needs capability of feeding the large constant current, standing on the high voltage,...
This paper deals with experience from comparative laboratory tests, carried out by Televerket - Swedish Telecommunications Administration - on different types of stationary lead-acid batteries for telecommunications applications. Examples are given on how experience has been used to increase quality and reliability in batteries. The test batteries have been kept under verified charge conditions for...
Research and experience have shown that cell voltage plays a significant role for the service lifetime of constantly charged high-antimonic lead batteries. It is generally believed that this also occures for newer types low-antimonic lead batteries. Since a battery charger keeps the total voltage at a constant level there will excist deviations between the individual cells. As a consequence of this...
Since 1978-1983 many photovoltaic systems for telecommunication purposes, village and house electrification, water treatment etc. have been installed. 15 pilot-plant funded by the European Community are in operation since 1982/83. First results will be given regarding the successfull operation, the maintenance and the lifetime of the batteries used in these installations. Design criteria will be discussed...
As the most widely used means to know the charged condition of a lead-acid battery, the method to measure the specific gravity of the electrolyte is adopted. Here we report in this paper on an optical-type sensor taking advantage of the fact that the sulfuric acid electrolyte has a certain definite refractive index in accordance with its specific gravity and the device applying such a principle. Several...
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