Samsung Ubigate iBG3026, Руководство по настройке

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CHAPTER 31. Digital Voice Port
512
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T1 CAS Signalings
CAS stands for Channel Associated Signalling and various types of CAS
signaling are available in the T1 world. The most common forms of CAS
signaling are loopstart, groundstart, and E & M signaling. These protocols
provide information such as the number that was called, and what state the call
is in. They’re limited in what information they can carry, and are slow to set up.
With this kind of signalling, a set of bits is used to replicate opening and
closing the circuit(as if picking up the telephone receiver and pulsing digits on
a rotary phone), or using tone signalling which is passed through on the voice
circuits themselves
The biggest disadvantage of CAS signaling is that the network uses bits from
information IP packets, such as voice packets, to perform signaling functions.
CAS signaling is often referred to as robbed-bit signaling.
Digital T1 trunk to be used in connection of most switch-to-switch is E & M
signaling type, but there is the case partially forming connection with FXS and FXO.
Figure 31.8 T1 CAS signaling network
1.
Loopstart signaling
Is the simplest type of CAS signaling, which change the operation type of
analog FXS into digital signaling type as it is. Thus, there are more defects
than other CAS signaling.
PSTN
PBX, K/P
T1-R1, T1-FXS
T1-FXO, T1-E & M
T1-R1, T1-FXS
T1-FXO, T1-E & M