Nortel-networks Circuit Card Manual de usuario descargar pdf (Pagina 52)

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Page 52 of 906 Overview

553-3001-211 Standard 3.00 August 2005

Ground Start Mode

In ground start mode, the A and B bits have the following meaning:

Transmit from LTI:A bit = Tip ground (0=grounded, 1=not grounded)

B bit = Ringing (0=on, 1=off)

Receive to LTI: A bit = Loop (0=open, 1=closed)

B bit = Ring ground (0=grounded, 1=not grounded)

When a T1 channel is idle, the lineside T1 card simulates a ground on the tip

lead and -48V dc on the ring lead to the terminal equipment by setting the

transmit A bit to 1 and transmit B bit to 1. Accordingly, an on-hook telephone

simulates an open loop toward the lineside T1 card, causing the lineside T1

card’s receive bits to be set to A = 0 and B = 1.

• Steady state (call in progress) 0 1 1 1

• Far end disconnects by dropping loop current and lineside T1

card changes Transmit A bit to 1 momentarily.

1 1 1 1

• Terminal equipment responds causing Receive A bit to

change to 0.

1 1 0 1

• Lineside T1 responds by changing its Transmit A bit to 0. Call

is terminated and set to idle state.

0 1 0 1

Call disconnect from terminal equipment:

• Steady state (call in progress) 0 1 1 1

• Terminal equipment goes on-hook causing the Receive A bit

to change to 0. Call is terminated and set to idle state.

0 1 0 1

Table 4

Loop Start Call Processing A/B Bit Settings (Part 2 of 2)

State

Transmit Receive

A B A B

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 907 908

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Nortel-networks Circuit Card Manual de usuario Pagina 52

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