It can be said that power cable transmission has hitherto been restricted to shipping companies with a high proportion of refrigerated containers. There is no evidence of all refrigerated containers being generally equipped with modems. Two different systems will still be deployed, which means that the evaluation installations used on ships and terminals must be able to cope with both systems for the foreseeable future in order to effectively exploit the savings potential. Even if it may seem that recent investments are generally being made in wideband, there are still too many narrowband containers to expect them all to be converted to wideband. In the long term, however, the modems of the first generation at least must be upgraded, since the impedance values are too low and this interferes with dual band line transmission.
Figure 24: Carrier MicroLink II refrigeration unit with integral RMC wideband slave modem
Until now, a number of major shipping companies have been operating their systems in relative isolation. Increasingly, they are realizing that when cooperating with other shipping companies, which use the other system, provisions need to be made to ensure that both systems can be used on all ships. This development is of course even more noticeable at the terminals.
A similar situation can be observed regarding the use of four-wire monitoring. It is to be expected that this technology will be replaced by power line transmission, but even then there would still be too many containers in circulation without PCT, but using four-wire technology instead, for it to be possible to give up this technology altogether.
It is expected that future technology will base on radio data transmission, as this promises higher transmission rates and lower susceptibility to interference.
Using satellites to monitor refrigerated containers generally fails, because when the containers are stacked they cover the antennas of the containers below them, thus making data transmission impossible. The same applies when containers are stowed below deck. In future, however, it will definitely be possible to send data transmitted by PCT via satellite from the ship to receiving stations on land, to enable the refrigerated containers to be accessed online.
When transmitting CA data (oxygen content, carbon dioxide content, humidity) by power line transmission, it will be necessary for the controller of the refrigeration unit to forward this data to the slave modem and for the evaluation software to be able to process this data accordingly.
Figure 25: ThermoKing refrigeration unit with integral RTE wideband slave modem

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