Loop Start Trunk Signalling

by Peter Moorey under
Loop start signalling - telephony informational signalling
Typically used by local loops when connecting to residential phones

Three states, idle (on hook), telephone seizure (off hook), CO seizure (ringing).



















Disadvantage of loop start is that both CO and telephone can seize the trunk at the same time (glare).
Posted by Peter Moorey at 00:41 0 comments
Labels:

Trunk Line Types

by Peter Moorey under
Private Trunk Lines (tie-lines) - PABX to PABX - E&M interfaces
CO Trunk Lines - PABX to CO switch
Interoffice Trunks - CO to CO switch trunk (inter-CO-office)

Foreign Exchange (FX) Trunks:
FXO - extending a phone line to a PABX, Cisco router or telco
FXS - connections telephones, faxes and modems (end-points)

Posted by Peter Moorey at 07:24 0 comments

Trunk Line Basics

by Peter Moorey under
In modern communications, trunking is a concept by which a communications system can provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually.


E1 - 2048Kb/sec - 32 channels (64Kb/sec) - Common Channel Signalling - Out-band
Channel 0 E1 sync/error checking
Channel 1-31 DS0 channels for voice

T1 - 1544Kb/sec - 24 channels (64Kb/sec) - Common Channel Signalling - In-band
Channel 0-23 DS0 channels for voice (robbed bit from each channel for signalling/error checking)

ISDN PRI over E1 - 2048Kb/sec - 30 channels (64Kb/sec) - Channel Associated Signalling - Out-band
Channel 0 E1 sync/error checking
Channel 1-15 DS0 channels for voice
Channel 16 ISDN D signalling
Channel 17-30 DS0 channels for voice

ISDN PRI over T1 - 1544Kb/sec - 23 channels (64Kb/sec) - Channel Associated Calling - Out-band
Channel 1-23 DS0 channels for voice
Channel 24 ISDN D signalling
Posted by Peter Moorey at 14:35 0 comments

Private Branch Exchange (PBX) and Key system

by Peter Moorey under
PBX
- Scales highly >50 users
- Typically digital end-points, Propriatory to PBX manufacturer
- Trunks to PSTN

1. Terminal interface (lines, handsets, trunks)
2. Switching network (enables path between end-points)
3. Control Complex (logic, memory, call processing)

Key System
- Less scaleable
- Propriatory to PBX manufacturer
- 'Shared' trunk lines
Posted by Peter Moorey at 14:06 0 comments

Central Office (CO) Switch

by Peter Moorey under
- Interfaces local-loop (end-points), trunks to CO's/PBX

1. Battery - power to local end-points -48v DC off-hook, AC voltage on-hook (ringer)
2. Current detector - detects off-hook closed circuit
3. Dial-tone generator - after off-hook detection dial tone is provided
4. Dial-register - receives dialed digits (pulse/DTMF) from end-point
5. Ring generator - incoming call, generates ring tone (AC voltage) to end-point


Typical CO
Posted by Peter Moorey at 13:40 0 comments
Subscribe to: Posts (Atom)
Copyright © 2010 Cisco Voice over IP (CVOICE) All rights reserved.
Wp Theme by Templatesnext . Blogger Template by Anshul