This paper researches changing of some basic parameters of symmetrical copper based twisted pair which is near the other twisted pair where active ADSL service exists. Analyzed parameters are: attenuation, signal to noise ratio, wideband noise and characteristic impedance. Analyzed subject is one pair in cable whose capacity is 100 x 2 x 0.4, with foamed polyethylene insulation and laminated polyethylene sheath. Existing ADSL service is sent through the different pairs in the observe cable and changes of the treated pair parameters are measured depending on the distance of the existing ADSL service from it. Obtained results are compared among themselves and with the parameters which are obtained in absence of ADSL service.

This paper is analyzing how some symmetrical-cooper-twisted-pair parameters take effect to of ADSL services. The treated parameters are insulation resistance, hop resistance and attenuation (on several significant frequencies). As the parameter of quality of service the bit-rate (both up-stream and down-stream bit-rate) is used. The testing transmission line is twisted pair placed in low-band telecommunication cable, with variable length (up to 8000 meters), and with 0.4 mm conductor diameter. We treated two types of low-band telecommunications cables-cable with paper-based insulation and lead-shield (approximately 25 years old), and cable with polyethylene-based insulation and aluminium-shield (2.5 years old). Basic theory of electrical loops is given at begin, measurements results and conclusion follow after that