Operation
Micron Modem
0630-SOM-00001, Issue: 03
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© Tritech International Ltd.
second unit. The operating distinction between a master and slave is that each uses a
separately coded CHIRP to avoid a unit receiving a close echo of its own transmission.
• The Micron Data Modem acoustic communication link provides a serial data transmission
path through water.
• The Micron Data Modem has an internal buffer of 256 bytes. The incoming serial data rate
must take into account of the acoustic transmission rate of 40bit·s
-1
and this buffer size.
• The acoustic radiation pattern is approximately omni-directional, and the modem will
operate in both horizontal and vertical attitudes.
• Data modems should not be placed close to any acoustically reflecting surfaces, such as
a boat hull or the sea/seabed surface, ideally providing a separation of at least 1m.
• Each Micron Modem is capable of withstanding Doppler shifts of up to ±5m·s
-1
.
• No unique addressing function is provided. A slave modem can communicate with a master
modem only, with a master modem capable of broadcasting data to all slave modems
within operational range.
• Data control is not provided by the Micron Data Modem. For instance simultaneous
transmissions from both modems in a pair may not result in transmission receipt by either
modem. Control of the Micron Modem must be handled by the connected computer or
hardware.
• Error checking and data quality is not provided by the Micron Modem. Any error in
transmission will not be detected by the Modem and the Modem will not attempt re-
transmission of the same data should it not be received correctly by the receiving Modem.
• The RNG function command can be used to calculate the distance acoustically between
the two Modems with an accuracy of ±0.2m
4.3. Transmission Characteristics
Transmission characteristics are depended on a variety of operating conditions which can
significantly reduce operating range:
• The presence of thermoclines
• The presence of acoustically reflecting surfaces within the operating environment
• Ambient noise
• Salinity
• Volume reverberation
• Surface and seabed reflectivity
• Significant Doppler shifts present, due to the relative movement between two
communicating Modems.
