Line Charged Batteries to Power Telecommunications Equipment

The non-availability of mains power at remote locations or in consumers´ premises where connection to the local mains supply would be difficult, are typical applications for line-powered telecommunications equipment. However, due to the limitations of line current, a local battery is required. Sealed Nickel Cadmium button cells have been used in such applications for many years. This paper will discuss the ability of batteries to accept the very low rates of charge which are necessary when batteries are required to share the limited line current with the telecommunications equipment. Typical applications include outband signalling equipment such as line-sharing apparatus, where the local battery powers the outband equipment when the solid copper pair is in use, or any equipment which requires large pulses of current which the line cannot supply, such as payphones which sort money to give change. For the future, subscribers in ISDN systems, will require local power UPS where line charging will not be possible.