Negative impedance repeater for telephone lines

Claim 1

A negative impedance repeater for amplification of loaded or non-loaded telephone lines operating at voice frequency comprising: a first open circuit stable one-port network, the terminals of which are the input terminals of a negative impedance converter, the output of which is loaded by a preset passive impedance network, chosen in relation to the characteristic impedances of the line section to be amplified; a second short circuit stable one-port network, the terminals of which are the input terminals of a negative impedance converter, the output of which is loaded by a preset passive impedance network, chosen in relation to the characteristic impedances of the line section to be amplified; adjusting means in each of said converters, and external to said impedance networks, for adjusting the feedback and consequently the conversion ratio; said adjusting means being independent from each other and being manually varied on the basis of predetermined conversion ratio curves such that: in the case of loaded lines, the product of the two conversion ratios remains constant over the entire variation range; to provide a gain adjustment which does not affect the repeater impedance and in the case of non-loaded lines, the conversion ratio of the converter included with the short circuit stable network increases quicker than the conversion ratio of the converter included within the open circuit stable network decreases, to provide a gain adjustment which increases more quickly at the high frequencies than at the low frequencies of the transmitted band, so that an equalization, necessary for this type of lines is introduced, and, coupling means for coupling said converters to the line to be amplified.