Samsung Ubigate iBG3026 Configuration Manual page 496

CHAPTER 30. Analog Voice Port
Loop Start Signaling
Loop-start
Hooking off handset makes a circuit close, and off-hook status is detected,
while submarine sends dial tone. Also it sends on/off pattern ring to receive
dial tone.
1) Idle state
2) Hook-Off state
Ground Start Signaling
It works by using ground and current detectors that allow the network to
indicate off-hook or seizure of an incoming call independent of the ringing
signal and allow for positive recognition of connects and disconnects.
For these reasons, ground-start method is used as inter-PBX Trunk line.
454
is generally used in Analog FXS/FXO instead of Ground-start.
Analog FXS Interface or
module in submarine
Ring
Generator
-48DC
Battery
Analog FXS Interface or
module in submarine
Ring
Generator
-48DC
Battery
Figure 30.1 Loop Start Signaling
Telephone set or PBX
Tip
Ring
Telephone set or PBX
Tip
Ring
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Opened
(loop broken)
Closed
(loop hold)