August 2012 – Ed.1.2
EQUITEL – E451 Technical manual
Page 13
Chapter 3
Functionality
In this chapter we will detail the IP intercom System functionalities based on the modules E451.
We will explain separately each one of the possible operation modes in which E451 can be configured; the event
chains taking place in each case; the pre-recorded audio messages used,…
3.1
Proprietary mode
3.1.1.
Connection with the controller
In this mode, the communication establishment between E451 and the controller is made through an
EQUITEL proprietary protocol. It is described in the document “Communications protocol E400 EQUITEL
family”, where it is detailed all the information regarding the communication functioning between the
E451 and the controller.
E451 behaves as a TCP server in the port
7000
and accepts one single client connection at the same time.
3.1.2.
Sending a call
Once the user button is activated, the process of sending the call to the control centre begins as per the
following sequence:
1.
E451 sends a TCP message to the controller indicating that the push button has been activated
and requests a call, “DEMCALL”.
2.
The controller will answer with the corresponding ACK, in this case “ACK_DEMCALL”.
3.
When the previous ACK message is received, E451 begins to play the prerecorded message
“
calling tone
”,
indicating “called received” and will remain like that for a maximum of 1 minute
waiting to receive the audio activation message from the central. While playing, the status LED
(see Figure 3) will light intermittently.
4.
In case of not receiving the ACK, or if one minute has passed by and the audio has not been
activated, E451 will play twice the pre-recorded message “
offline tone
” which indicates
“destination not available” and the LED will turn off.
3.1.3.
Audio communication establishment
When a controller wants to establish audio communication with E451, either as a result of call or
asynchronously, the former sends a message of “STARTAUDIO” to E451, in which it is included the IP
address and the audio destination port.
The moment E451 receives this order, it opens the port
30000
to listen to the incoming RTP packets and
sends what it generates to the indicated address and ports.
E451
answers
the
controller
with
the
corresponding
ACK
(“ACK_STARTAUDIO_OK”,
“ACK_STARTAUDIO_NOK”), indicating whether it has been possible to activate the audio or not.
If the audio activation has been correctly made, the LED will light and will remain like this as long as the
audio keeps open.
Should error communications arise, in order to avoid E451 to have the audio permanently activated the
controller sends refresh orders. Every time the order “STARTAUDIO” is received, the audio
communication will remain active for a maximum of 2 minutes.
The audio communication with E451 uses the RTP protocol with the codification G.711-A and a sampling
frequency of 8 kHz.
