Nortel Networks 553-3001-211 manual Outgoing calls

Page 168 of 894 NT1R20 Off-Premise Station Analog Line card

Table 67

Call connection sequence—near-end station receiving call (Part 2 of 2)

	Signal / Direction
State	Far-end / Near-end	Remarks
Far end station	High resistance loop	If the far-end hangs-up first, the system
hangs up first		detects disconnect signalling from the
		trunk. The person at the near-end
		recognizes the end of the call and
		hangs-up.
Line card unit idle	Ground on tip/battery on ring	Line card unit is ready for the next call.
	High resistance loop

Outgoing calls

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 68 on page 168). When 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.

Table 68

Call connection sequence—near-end station receiving call (Part 1 of 2)

	Signal / Direction
State	Far-end / Near-end	Remarks
Line card unit idle	Group on tip, battery on ring	No battery current drawn.
	High resistance loop
Call request	Low resistance loop	Near-end station goes off-hook. Battery
		current is drawn, causing detection of
		off-hook state.
	Dial Tone	Dial tone is applied to the near end
		station from the system.

553-3001-211 Standard 2.00 September 2004