Electrical transmission or interconnection systems – Personnel safety or limit control features – Interlock
Patent
1979-10-15
1981-10-20
Mullins, James B.
Electrical transmission or interconnection systems
Personnel safety or limit control features
Interlock
328147, H03K 524
Patent
active
042963370
ABSTRACT:
The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a large plurality of subscriber loops.
REFERENCES:
patent: 3339027 (1967-08-01), Feiner et al.
patent: 3403228 (1968-09-01), Zebe
patent: 3671676 (1972-06-01), Henry et al.
patent: 3784756 (1974-01-01), Nemchik
patent: 3816668 (1974-06-01), Giesken
patent: 4056688 (1977-01-01), Stiefel
patent: 4129118 (1978-12-01), Banke
Bell Telephone Laboratories Incorporated
Mullins James B.
Nimtz Robert O.
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