Nortel Circuit Card Installation Manual page 170

Page 170 of 906
Table 68
Call connection sequence—near-end station receiving call (Part 2 of 2)
State
Far end station
hangs up first
Line card unit idle
Outgoing calls
Table 69
Call connection sequence—near-end station receiving call (Part 1 of 2)
State
Line card unit idle
Call request
553-3001-211 Standard 3.00
NT1R20 Off-Premise Station Analog Line card
Signal / Direction
Far-end / Near-end
High resistance loop
Ground on tip/battery on ring
High resistance loop
For outgoing calls from a telephone, a line unit is seized when the telephone
goes off-hook, placing a low-resistance loop across the tip and ring leads
towards the NT1R20 OPS analog line card (see Table 69 on
the card detects the low-resistance loop, it prepares to receive digits. When
the system is ready to receive digits, it returns a dial tone. Outward address
signaling is then applied from the telephone in the form of loop (interrupting)
dial pulses or DTMF tones.
Signal / Direction
Far-end / Near-end
Group on tip, battery on ring
High resistance loop
Low resistance loop
Dial Tone
August 2005
Remarks
If the far-end hangs-up first, the system
detects disconnect signalling from the
trunk. The person at the near-end
recognizes the end of the call and
hangs-up.
Line card unit is ready for the next call.
Remarks
No battery current drawn.
Near-end station goes off-hook.
Battery current is drawn, causing
detection of off-hook state.
Dial tone is applied to the near end
station from the system.
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