Abstract: A navigation guidance system is provided which gives direction information from a remote server to a mobile user unit for guiding the user from their current location. The user unit may be a mobile telephone, PDA or the like. A navigation query is transmitted from the user to the remote server. A GPS receiver or the like is provided so that the current location of the mobile unit can also be determined and provided to the remote server. Based on the information received from the user, the server determines appropriate route guidance information and sends this back to the user. In a preferred form of the invention, the data is transmitted between the user unit and the remote server using DTMF tones which are encoded so that no two consecutive tones are identical.