Network Topology; 4X4 Acu Network Topology - ASL INTERCOM VAR8 Product Description

The audio bus has a 30 Hz surveillance signal superimposed on the normal VA audio. This surveillance tone
is monitored at each Slave Unit, and enables the Slave Units to report fault in the network.
As soon as any audio faults are reported the system goes into fault recovery sequence, which, in essence,
isolates the Slave Units at each side of a potential cable fault until the fault is pinpointed. Once this is done
the faulty segment remains isolated and the audio from the Audio Control Unit is transmitted in both
UPSTREAM and DOWNSTREAM directions to the slaves.
As well as distributing the audio, the Master Fire Microphone's Press To Talk signal is conveyed over the
audio link using special circuitry not involving the processing circuits. This fulfils the BS5839 requirement that
'All-Call Fireman's Microphone' operation is supported even if control processor or data network fail.
3.2

Network Topology

Two types of network topology are available:
•

4x4 ACU Network Topology

The network is hosted by a 4x4 Intellevac ACU Audio Control Unit and assumes the 4x4 architecture. It
is the original system and is considered the legacy network.
•
8x8 ACU Network Topology
The network is hosted by an 8x8 Intellevac ACU Audio Control Unit and deploys the Enhanced Network
Protocol, which enables any combination of Intellevac DAU Distributed Amplifier Units and VAR Routers
as Slave Units. Therefore the 8x8 ACU Network enables wall mount and rack mount systems in the
same network adding flexibility to the network configuration.
The 8x8 Audio Control Unit can be either a wall mount 8x8 Intellevac ACU Audio Control Unit or a rack
mount VAR8-ACU Router.
The network topology and capabilities are different as described in the following sections.
Data on the original 4x4 Intellevac units is included for reference only. Only 8x8 Intellevac units
are available for ordering.
3.2.1 4x4 ACU Network Topology
The original 4x4 Intellevac ACU supports the following Slave Units:
•
Wall mount Intellevac Distributed Amplifier Units, both legacy 4x4 DAUs and 8x8 DAUs.
•
Rack mount VAR8 Routers fitted with Network Interface Card.
From the network perspective, an 8x8 unit is a 4x4 Slave Unit.
The Audio Control Unit normally 'talks' out of its UPSTREAM port, which is connected to the
DOWNSTREAM port of the first Slave Unit in the chain. The UPSTREAM port of that Slave Unit is then
connected to the DOWNSTREAM port of the following system until a complete 'ring' is implemented back to
the Audio Control Unit.
The first Slave Unit is allocated a Slave-ID of 1, the next unit has Slave-ID 2 etc. The Slave-ID corresponds
to the Slave Unit's physical position in the network.
All outputs from the Slave Units then become a contiguous sequence from the Audio Control Unit point of
view:
•
Slave-ID#1: outputs 1 to 4
•
Slave-ID#2: outputs 5 to 8
•
Etc.
Figure 9 shows the scheme of an Intellevac Network of DAU (4x4 and 8x8) and VAR8 units hosted by a 4x4
Intellevac ACU.
VAR8 and Variants - Product Description
Issue: 02 complete, approved
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