Eicon Networks ISDN NT1 Spécifications télécharger pdf (Page 37)

When there is more than one device capable of receiving the incoming call at the

destination, a mechanism exists to ensure that only one device can answer.

The SETUP is broadcast to all devices at the destination, and they in turn respond with an

ALERT.

At this point, both devices are "ringing".

In this example, the upper device answers the call - a user picks up the telephone. This

stops the bell ringing.

What about the lower telephone? Its bell is still ringing.

Stop other devices ringing

Since the network is aware of which device successfully answered the call, and also which

devices have expressed an interest in the call, it is able to send a REL message to all

those devices which sent an ALERT but did not answer. This stops these devices from

ringing (or whatever is the equivalent activity for the type of device in question).

The interesting point about this scenario is that devices sharing the same line

communicate with the network. They do not communicate with each other. In fact, they

are unaware of the existence of each other.

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Eicon Networks ISDN NT1 Spécifications Page 37