August 2012 – Ed.1.2
EQUITEL – E451 Technical manual
Page 14
3.1.4.
Audio communication closing
To close an audio communication previously established, the controller must send the message of
“STOPAUDIO”.
E451 will send the corresponding ACK (“ACK_STOPAUDIO_CLOSED”, “ACK_STOPAUDIO_NOCLOSED”). This
way, the controller will be able to know if the unit has the audio closed or not.
The LED switched off indicates that the audio circuits are correctly closed.
3.2
SIP mode with PBX
E451 incorporates a SIP agent that allows receiving and making calls directly to SIP devices, and even to
analogue or mobile devices if the appropriate PBX is used.
This protocol encompasses the establishment, modification and finalization management of multimedia
services interchange sessions among several participants through digital networks.
SIP is a very complex protocol since it covers several aspects, and in E451 we have given the application of
VoIP calls management. We have implemented a small part that allows answering and making calls to the
configured device by means of a “push-to-call” function associated to the user button (see Figure 3).
E451 may register in a SIP PBX as another extension to make and receive calls. Furthermore, it supports calls
forwarding, so that (for example) the call received in an intercom can be forwarded to another extension.
Figure 11.
Basic network for a E451 using SIP
Through this system, it would be possible to implement an IP intercom network by using E451 units with the
need of a controller; it is simply required a SIP PBX and one or several telephones.
