NMEA Data Pacing

The NMEA standard recommends that NMEA sentences produced by individual instruments are sent at a frequency not higher than once per second. Some instruments, especially some electronic compasses and engine function sensors, send their NMEA sentences at much higher frequencies. This can cause serious congestion in integrated instrument/computer systems, especially if these sentences are combined with data from other NMEA talker sources. The amount of data to be processed by the computer software can be so large that it slows down significantly and some programs stall.

Many of the values contained in sentences sent at these high frequencies change very little from one sentence to the next. For example, it is unlikely that the vessel's heading changes much in half a second time. The same heading value is likely to be sent repeatedly over and over again.

The Data Pacing mechanism in Brookhouse NMEA Multiplexers, if activated, blocks data received from a selected port  for short periods, to insert time gaps in the data stream and give the computer or other NMEA listener some "breathing space". For example, one second interruptions can make a considerable difference and alleviate the system load whilst it is unlikely that the sentences suppressed during that single second will contain significant changes. After a block period, sentences are allowed through again for a short period of time.

The block period always starts after a complete sentence has been received and when after the time-out data is sent through again, it will always start with the beginning of a new sentence ($).

Together with the filtering feature, data-pacing allows the user to fine-tune and optimize the integrated instruments/computer system to the maximum.

Data-pacing is activated from the mux set-up menu, but if only the standard mux functionality is required, nothing has to be done, as with other advanced  multiplexer features.