ID3000 Series Installation & Commissioning Manual
A4 - 2997-274-000-6, Issue 6
September 2009
Appendix 4
2 Functional Description
The peer-to-peer architecture is based on the
ARCNET
®
protocol which is ideally suited to fire
detection and control applications.
Fundamentally, all network messaging is under
the control of ARCNET’s proprietary Invitation-
to-Transmit (ITT) or ‘token-passing’ protocol.
The token-passing method facilitates fast and
predictable network message transmission
times. This predictable aspect of the token-
passing protocol is important when there is a
need to demonstrate that specified networking
performance requirements can be met.
NOTIFIER Fire Systems has expanded on this
philosophy by implementing a separate network
between each fire control panel. Each Network
Gateway Module (NGM) on the ID
2
net includes
two ARCNET
®
microprocessors, where each
is capable of working independently of the other.
This allows a networked fire control panel to
communicate simultaneously with the panels
either side of it. The drawing at left shows eight
panels networked together in a continuous loop
arrangement.
It can be seen that, conceptually, total
networking of all eight panels is achieved
through an arrangement of two-node networks
to provide the physical inter-panel
communication. For example, while panel B
transmits/receives a message to/from panel A
it can simultaneously transmit/receive a
message to/from panel C. The independent
token passing protocol between panels A and
B and B and C makes this possible.
Error checking of each message is carried out,
using ARCNET’s built-in Cyclic Redundancy
Check (CRC), and signal distortion is removed
before onward transmission. This
‘regenerative’ approach ensures the integrity
of message data, especially over long
distances. Further error-checking is carried out
within the panels.
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