The Range Extender with Gain - A New Telephone System Loop Extender

Approximately 2 percent of Bell System loops are longer than the central office switching equipment design limit of 1300 Ω. These long loops require treatment on a special basis with the use of so-called long line circuits and voice frequency repeaters. The complexity, cost, and lack of a simple way to test the loop through these circuits led to a new design. In this paper, we describe the REG, an integrated signaling Range Extender with a voice frequency Gain unit which overcomes these shortcomings. The key to providing the improved features is a novel electronic dual-mode current detector. The requirements and design of the current detector are covered in detail. Finally, we discuss REG operation illustrating the problems of the switching system interface.