ISO 10368 standard
Experience has proved that it only makes sense to use a monitoring system when there is a standard for data exchange, as genuine saving effects can only be achieved if all refrigerated containers can be monitored by PCT insofar as this is possible. For this reason, an ISO sub-committee was set up between 1987 and 1990 to define a standard. This was finally published as ISO 10368. Since the various companies participating in the committee had different interests, no consensus was reached regarding hardware (i.e. the transmission frequency), and consequently there are still two systems available on the market. Only the frequency ranges for each system were defined, to ensure that they could both be operated simultaneously.
Apart from this, the standard primarily regulates the data transmission protocol (i.e. software) and defines the minimum range of functions for remote communication devices (RCDs).
These functions comprise:

Prescribed queries:
  • Identification number of the container or clip-on unit

  • Porthole container number (for porthole containers refrigerated with a clip-on unit)

  • Date and time of any change to the porthole container number

  • Current return air temperature

  • Current supply air temperature

  • Manufacturer/type
Important optional queries (list not complete):
  • Operating mode (Full Cool, Partial or lower capacity cool, Modulated Cool, Fans only, Defrost, Heat)

  • Nominal temperature

  • Alarms (status query)

  • Current alarms (in the order in which they occurred)

  • Product temperatures

  • Data logger interval

  • Power consumption

  • Port of destination of the container

  • Port of discharge

  • Origin

  • Results of the self-check (PTI)
Commands for controlling and programming (insofar as the controller of the refrigerated unit supports them):
  • Change the nominal temperature

  • Start self-check (PTI)

  • Change the identification number

  • Change the data logger interval

  • Set the date and time of the data logger

  • Change the operating mode

  • Download data logger information

  • Change the porthole container number

  • Change the destination
Precise data protocols were not defined for all commands and room was left for subsequent extensions in the form of "private sessions", which can be used by individual manufacturers to transmit proprietary data. This extension facility was used excessively by certain manufacturers, to the extent that many functions available today are transmitted within these non-standardized protocol sections. There is disagreement on which of the protocols should put in the public domain and therefore available to the competition for this type of transmission, and under what conditions.
Overall, the ISO Standard has only documented the two existing systems and prescribed some very basic queries. Even if all transmission protocols were put in the public domain, this would mean today that a separate software driver would have to be available for every modem type. Since the controllers of the refrigeration units and the data loggers which are used also have different ranges of functions and data formats, a large number of drivers is needed to support all potential configurations. Consequently, the ISO Standard has been of little help and only resulted in apparent standardization.
Another issue which was not dealt with by ISO is data protection. In accordance with ISO (and also in practice), all data on all containers equipped with modems is available on the power supply network. It is therefore possible theoretically that third parties with access to the power line network via a master modem can read out and even change information on the containers (e.g. the nominal values). This was never a problem while shipping companies were only using PCT on board their own ships and terminals. Once it began to be used on multi user terminals, however, the network operators (terminal operators) have had to ensure that only authorized persons have access to information on containers which pertains to them.

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