Abstract: An inband signaling modem communicates digital data over a voice channel of a wireless telecommunications network. An input receives digital data. An encoder converts the digital data into audio tones that synthesize frequency characteristics of human speech. The digital data is also encoded to prevent voice encoding circuitry in the telecommunications network from corrupting the synthesized audio tones representing the digital data. An output then outputs the synthesized audio tones to a voice channel of a digital wireless telecommunications network.

Abstract: In the case of a conventional radio telecommunication system for transmitting information between stationary transmitting/receiving units and mobile transmitting/receiving units it is proposed that the mobile units be additionally provided with a satellite navigation receiver for independently determining a position rough value. The stationary units are likewise provided with a satellite navigation receiver for independently determining a reference position rough value of a reference location of known exact geographical position as the reference position normal value, and with an error detection unit for detecting position determination errors by comparing the instantaneously determined reference position rough value with the reference position normal value.