NTT has successfully developed a common terminal capable of transmission and reception through dual-mode function for both the PHS and GSM systems.
This common terminal offers features combining the advantages of both PHS and GSM. It has automatic access to PHS (within PHS itself, the cordless telephone gives priority to the public PHS), and then to GSM, depending on the signal condition in the place where it is being used.
In the countries or areas where GSM is already in use, there will be a need for the services to be made available with a single terminal compatible with the both systems, to cope with constant shortage of frequencies in urban districts, to enable telephone services even in underground malls, and to ensure a lower air-time charge. It is also expected that a need will arise for a combined GSM and PHS cordless telephone at home and in the office.
As one of the attempts to address these needs, NTT has made a prototype dual-mode terminal and confirmed with a system simulator that it can be used with the hybrid PHS/GSM system at a satisfactory quality level.
This prototype terminal is expected to help develop the PHS system in countries where GSM is already available.
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http://www.nttinfo.ntt.co.jp/NR/1997/3_6est.html