Document: LT0732 QE20 Fibre Networking User Manual
Issue 1.0 24 May 2023 Page 4-1
4. VIF0907 Module
VIF Function
The VIGILANT VIF module is designed as an interface between the QE20 and a 3
rd
party VoIP ATA. The ATA is used to provide QE20 “backbone” (inter-panel) audio
communications by converting the QE20’s audio circuits into digital data and
transmitting this between the appropriate panels (one-to-one calls), and the PIB VoIP
proxy (one-to-many calls).
The ATA usually provides a means to connect an analogue telephone onto an IP
network. It decodes DTMF tones to obtain the dialled digits, then communicates with
a SIP server to obtain the IP address of the remote VoIP interface to connect to.
However, for the QE20, no SIP server is used, and the ATA is instead configured to
internally convert dialled digits to an IP address:port and then call that IP
address:port directly (which will be that of another ATA or a PIB VoIP proxy on the
QE20 network).
4.1.1 VIF to ATA Interface
The connection point for the VIF to the ATA is the same as for connecting an analog
phone directly to the ATA.
Therefore, the VIF has been designed to emulate an analogue phone, i.e., it makes
calls by going off-hook (drawing current) then dialling using DTMF tones. It answers
incoming calls by recognising a ringing voltage on the line and going off-hook
(drawing current).
Additionally, the VIF provides 2 x 5V outputs suitable to power up to 2 ATAs.
4.1.2 VIF to QE20 Interface
The VIF connects to the Speech (PA) and WIP terminals of the QE20 RS485
Network Module. The VIF also connects to the QEComms terminals on the RS485
Network Module, so that it can be controlled by, and send status to, the QE20
Controller. In particular the QE20 commands the VIF to ‘dial’ remote nodes as
required (i.e. when a Speech (PA) and/or WIP connection is required between
nodes).
If other audio signals – paging console, background music, etc, are being carried
over the fibre network they are connected to the WIP and PA terminals on the
additional VIF module(s) fitted.
4.1.3 Block Diagram
Figure shows the major functional blocks of the VIF0907. It has a microprocessor
that communicates with and is controlled by the QE20 ECM. The remaining blocks
make up two sections that are virtually identical; one for PA and the other for WIP.
Each of these sections has a transformer to provide isolation to the QE20, a DTMF
generator controlled by the microprocessor, a ‘current sink’ enabled by the
microprocessor, a ring detector that feeds into the microprocessor, and a relay
controlled by the microprocessor that enables it to connect to one of two ATAs.
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