TDMA
Time-Division Multiple Access. AIS uses TDMA across two dedicated VHF frequencies – AIS 1 (161.975 MHz) and AIS 2 (162.025 MHz).
Although Class A and Class B both use TDMA, Class A units use a Self-Organised TDMA (SOTDMA; Self-Organizing amongst Class A's) whereas Class B units use CSTDMA (Carrier-Sense TDMA, polite to Class A's). Class B's therefore determine free slots in the VHF wavelengths and decide when to transmit a report, enabling a ‘politeness’ factor, so as not to interfere or cause degradation of Class A signals.
The transmission of signals and information varies from every 2 seconds to every 3 minutes depending on the speed of the vessel; more signals at higher speeds.
Related Products
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Furuno FA-50 Class B AIS Transponder
RRP: $2,750.00
NOW: $2,549.00
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Raymarine AIS700 Class B AIS Transceiver
RRP: $2,189.00
NOW: $2,027.00