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9.4.2 FloodGuard
Note on FloodGuard: FloodGuard is a stream control mechanism that can be enabled/disabled
independently for each audio transmitter. FloodGuard throttles the transmitter when it no longer
receives control messages from the receiver, thereby preventing the transmitter from flooding
the network.
FloodGuard only works when enabled on both the transmitter and the receiver, and when the
transmitter sends to a unicast address.
When a transmitter is enabled, it opens a control receive port with the port number equal to its
source port number + 1. This port listens for control packets from the destination receiver. When
no FloodGuard packets come in during the time set for the FloodGuard throttle delay, the
receiver is expected to have disappeared (powered off, receiver disabled, network problem, etc.)
and the stream is 'throttled'. In throttled mode the transmitter - in order to contact the intended
receiver (again) - sends empty packets into the network at an interval determined by the
FloodGuard throttle interval parameter. After reception of a valid FloodGuard packet the
transmitter immediately resumes streaming.
9.5 Contact Closures
Contact Closures page: CC # input settings
CC inputs and outputs
The A-80 offers eight contact closure (CC) inputs, each of them capable of transmitting three
copies per signal. The inputs can be configured to stream CC signals to an i-NVR or to activate a
signal in the API, for example. The A-80 also has four contact closure outputs to connect with
PLCs or other telemetry systems. The CC output can be activated through the API or received CC
streams.
CC status
The receiver relays are normally open (fail-safe). Each CC input is sampled 100 times per
second. Changes are transmitted directly, so overall latency of the contact closure signals is <20
ms. To confirm, the actual contact closure status is transmitted every 100 ms; there is no further
forward error correction on these signals.