Abstract: A method for a cellular telephone automatic credit card calling system. In the analysis method, a series of program steps are provided for a digital signal processor (DSP) in the cellular telephone that activates the digital signal processor to listen to and analyze the received voice signals. The method may be considered as including three parts. (1) Tone detection method using the DSP to listen to the tone received from the calling card company. (2) Initializing the mobile phone for calling card use by selecting a default method on the ground of the telephone number of the calling card company. (3) Setting up a card call using the above mentioned tone detection (1), automatic insertion of "0" in front of the dialed number and call activation by a long press of the SEND-key. All of the three parts are manifested on the sequence of calling card process steps and implementation in the mobile telephone.