A switching converter with an LC output filter behaves as a loose-tolerance voltage-controlled current source if each switch closure is ended when switch current reaches an adjustable threshold. This converter is then combined with an external feedback to produce a precise output voltage.By generating a fixed voltage with a current source in this manner, the converter has many advantages including continuous protection of the switches, stable and equal load sharing when several converters are operated in parallel, inherent overload protection, automatic switch symmetry correction, and fast system response.

Abssirucsi-Range extension allows the No. 2 electronic switching system (No. 2 ESS) to serve subscriber loops out to 2500 SZ as part of the Bell System's unigauge plan. Rangeextender circuits provide both audio and dc gain for loops greater than 1300 SZ. These circuits have been designed specifically to be low cost, as small as possible, and to use minimum power. Network concentration allows 70 percent fewer range extenders to be provided than customer Lines served. All trunk, service, and test circuits that had to be modified to work range extended are provided on a standard basis in every No. 2 ESS office. This means that range extension can be provided in a No. 2 ESS office at very low cost; essentially the cost of the rangeextender circuits.

No abstract