tailieunhanh - GR-1089 HDSL A3 VOLTAGE

HDSL is a powerful, cost-effective, T1-based transport technology that leverages existing copper infrastructure and is, therefore, of great interest to both subscribers and service providers. It uses central office (CO) units at the carrier's office and remote units at the customer site and may, depending upon distance, require HDSL repeaters over the length of the copper span. The power needed to operate the repeaters and remote equipment is provided over the span itself, and must be handled safely for the protection of users and telephone company craftspersons | GR-1089 HDSL A3 Voltage Technical Brief Introduction Setting Standards HDSL is a powerful cost-effective Tl-based transport technology that leverages existing copper infrastructure and is therefore of great interest to both subscribers and service providers. It uses central office CO units at the carrier s office and remote units at the customer site and may depending upon distance require HDSL repeaters over the length of the copper span. The power needed to operate the repeaters and remote equipment is provided over the span itself and must be handled safely for the protection of users and telephone company craftspersons. Nobody cares more about the safety of telecommunications equipment than ADC Telecommunications but when it comes to setting safety standards the industry turns to Bellcore. GR-1089 is a detailed Bellcore specification covering among other things safe powering of facilities. Section 7 of the document defines levels of allowable electrical currents and voltages which may be applied to circuits and equipment depending on who will have access to the equipment. Class Al is the most stringent and applies to areas which may be contacted by the general public which is assumed to be unfamiliar with electrical hazards. Class A2 permits higher limits and covers those areas where non-specialized telephone company employees may have contact. Class A3 is the highest allowable level for voltages which may be contacted barehanded. It applies to those areas available only to telephone company craftspersons familiar with the appropriate precautions and applies to HDSL circuits and equipment. Ill GR-1089 HDSL A3 Voltage Technical Brief A3 Defined The A3 standard covers both DC and AC voltages however only DC applies to HDSL equipment. According to section of the GR-1089 standard the limits apply between each terminal and ground with all other terminals first open-circuited and then with all other terminals individually grounded. Terminal refers to any HDSL .