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NMT DMS (The Nordic Mobile Telephone Data and Messaging Service*)- The NMT Communicator showed the way for GSM
In 1990, the development of a new data transfer system for NMT was started, based on the inherent FFSK modulation used in the NMT system signalling. The inventor of the idea of DMS as well as the author of the specifications and the developer of the test equipment for DMS is Seppo Tiainen who at that time worked for Telecom Finland. The FFSK modem, present in each NMT mobile phone, got a new job. A new data transfer protocol, including scrambling, fast handshaking and robustness to bad radio signals, was defined as part of the NMT specifications. It was then possible to send and receive data and text messages on a handheld phone without any additional accessories. The original display and keypad of the phone were enough.
The first commercial DMS device was made by Spectronic, Sweden. The company (Per Siversson in person) got a valued award, Polhemspriset, for their new handheld communicator product. Data and speech could alternate on the same link. It was possible to select a piece of music from a list, then select it and listen to it immediately. The device could also operate as a wireless data terminal for reading emails etc. The Spectronic phone was used e.g. by the police and logistics companies in Sweden. In Finland, one application was functioning as a radio modem for outdoor posters including changing text display. The price, however, limited its use to special applications. The author, as a test user, used it to read emails on Nordic airports before the era of GSM data and SMS.
In Finland, DMS was used in oil delivery trucks and mobile online lottery terminals. The manufacterers for the equipment were Benefon and Lalla Oy..
There were other DMS brands like Ericsson and Nokia. - Please note the audio lines (RCA, in/out) on the DMS multimedia modem made by Lalla Oy. Both audio and data were present on the same connection.
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*Also: DMS = Data Mobile Station
by Seppo Tiainen
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