Ubigate iBG3026 Configuration Guide/Ed.00
© SAMSUNG Electronics Co., Ltd.
527
Although it is very common, problems can occur whenever automatic
answering equipment is used as the phone. Since there is no way for the CO to
tell the phone to hang up(go On-Hook), if the answering equipment never times
out then the circuit can be permanently seized. This is usually not a problem for
‘real’ phones, since the end user will realize that there is no one on the call and
hang up. This problem can be solved by using Ground Start signaling.
Ground Start
Ground Start signaling was originally developed to aid in resolving Glare.
In Loop Start the only way to indicate an inbound call from the network is to
Ring the phone. During a full 6-second ringing cycle there is a 4-second
period when the phone is not physically ringing. So how do you know whether
a PBX is trying to answer an inbound call or if it is trying to initiate a new
call? Ground Start eliminates this problem by adding an additional state(Tip
Closed) which tells the FXO circuit that there is an inbound call in progress,
even during the ‘quiet’ ringing cycle.
For outbound calls, the PBX(or FXO interface) must first seize the line by
applying ground to the Ring lead of the Tip/Ring pair(Ring Ground).
The CO(or FXS interface) now knows that the FXO is trying to make an
outbound call, and it will not terminate inbound calls on that circuit.
Digital Loop-Start signaling
In case of Loop-start signaling, it works according to the following state table.
Incoming Call
Sent
Received
State
a[f]
b[f]
a[b]
b[b]
Idle 0
1
0
1
Seizured 0
1
1
1
Outgoing Call
Sent
Received
State
a[f]
b[f]
a[b]
b[b]
Idle 0 1 0 1
Seizing
0 0 0 1
Seizure
Ack.
0 0 1 1
Seizured
0 1 1 1
Summary of Contents for Ubigate iBG3026
Page 1: ......
Page 16: ...INTRODUCTION XIV SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 32: ...TABLE OF CONTENTS XXX SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 34: ......
Page 64: ...CHAPTER 4 System Logging 30 SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 72: ......
Page 94: ...CHAPTER 7 WAN Interfaces 58 SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 110: ......
Page 156: ...CHAPTER 15 BGP 118 SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 178: ...CHAPTER 17 VRRP 140 SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 262: ......
Page 288: ...CHAPTER 23 Firewall NAT 248 SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 346: ......
Page 706: ...CHAPTER 36 Management 664 SAMSUNG Electronics Co Ltd This page is intentionally left blank ...
Page 718: ...EQBD 000026 Ed 00 ...