PairGain PG-Flex, Руководство пользователя

Страница: 19 / 168

Subscriber Drop Testing
11
Subscriber Drop Testing
The ability to test a subscriber drop is an essential element in the overall outside plant maintenance
strategy. PG-Flex supports this function using a dc (metallic) test pair between the remote terminal
and central office terminal. Using standard metallic access techniques and equipment, the
telephone company can access a specific subscriber drop and have a metallic test path back to the
central office equipment.
For subscriber drop testing from the CO, PG-Flex is able to select and connect any subscriber drop
to the metallic bypass test pair at the RT. PG-Flex extends this connection back to the COT where
it switches onto the metallic access bus or to the corresponding subscriber line on the COT channel
card.
The most common method of subscriber drop metallic access is through the central office channel
unit of the selected subscriber. Momentary placement and removal of +116 Vdc on the tip
conductor is recognized by PG-Flex as a metallic access request. PG-Flex provides the metallic test
path (Figure 8) while the termination of the test pair is dependent on whether a Pair Gain Test
Controller (PGTC) Interface Unit is installed. When -116 Vdc is momentarily placed then removed
from the tip conductor, PG-Flex restores all connections back to normal.
Metallic access can also be activated through an ASCII terminal connected to the Craft maintenance
port located on the front of the COT line unit.
Channel Unit Signatures
To ensure that the test system can identify a carrier channel unit, all channel units incorporate the
appropriate three-terminal dc signature resistances (Table 1) and conform to Bellcore’s
TR-NWT-000057.
Table 1. COT Channel Unit Signatures
Termination FLC-701, List 2
FLC-703, List 3 All Other COT POTS
Channel Units
Tip-Ring (open) 475 k
Ω
, 1%
Tip-Ground 162 k
Ω
, 1% 332 k
Ω
, 1%
Ring-Ground 162 k
Ω
, 1% (open)