Two Power Supply Systems for Small Telecom Switching Offices

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. When developing these systems, the operation- and maintenance performance and personal safety have been taken into special consideration. These power supply systems will frequently be placed where disturbances such as lightning and other transient voltages occur. Therefore the system design to prevent system failures caused by such disturbances is discussed. It is also discussed how the power supply systems are designed to obtain a nearly equal availibility to the telecom network for subscribers connected to an RSS and to a central switching office. The principles for the described two systems are intended to be used for other telecom systems as well, e.g at fiber optic transmission systems.