Table of Contents
Advertisement
2-6 NT5K18 Exchange Line Trunk Card
Loop start operation
553-3001-173 UK Trunk cards description
United Kingdom
United Kingdom
United Kingdom
United Kingdom
United Kingdom
United Kingdom
Call placed by Meridian 1
The Meridian 1 places a call by applying ground to the B wire and the
Public Exchange acknowledges by applying ground to the A wire. The
Meridian 1 then places the trunk unit into the on-line state (low impedance
loop), and removes the ground from the B wire. When the Public
Exchange is ready to receive digits, it returns dial tone. The Meridian 1
sends digits in the form of Dual Tone Multifrequency (DTMF) tones or
dial pulses.
Public Exchange disconnects first
The Public Exchange disconnects a call by removing the ground on the A
wire of the trunk. The Meridian 1 detects the drop in current and responds
by returning to the idle state.
Meridian 1 disconnects first
The Meridian 1 disconnects a call by removing its on-line state and
drawing only a very low current from the A and B wires.
Loop start operation is configured in software and is implemented in the
card through software download messages.
Idle state
When the Exchange Line trunk is idle, it provides a high impedance toward
the public exchange for isolation and dc detection. The public exchange
applies -50V dc on the B wire of the trunk and ground on the A wire.
Call placed by Public Exchange
The public exchange initiates a call by applying ringing to the B wire and -
50 V dc to the A wire. The Meridian 1 ringing detector is tripped and the
Exchange Line trunk card place a low resistance dc loop between the A and
B wires. This low resistance loop serves as a called subscriber answer
signal (CSA) to the public exchange. The public exchange responds by
removing the ringing signal and returning the A and B wires to their
normal conditions.
Call placed by Meridian 1
To place a call from a telephone set or attendant console, the Meridian 1
places a low resistance loop across the A and B leads. When the public
exchange is ready to receive digits, it returns dial tone. The Meridian 1
Advertisement
Table of Contents
