publication_number US 5787180 A abstract an apparatus and method for voice privacy for cellular phones includes generic connection points to make it universal for most cellular phones the connection points include the speaker and microphone and the microphone input and speaker output of the cellular phone a scrambling or encryption circuit or process is used to secure the audio before it is transmitted over the network and the unsecured audio once received side tone added by the cellular phone and network echo of the scrambled audio to be transmitted is removed by for example adaptive echo cancellation and unscrambled side tone is presented to the speaker the apparatus can be implemented in a digital signal processor application_number US 82608397 A description to assist in a better understanding of the invention a description of one embodiment or form the invention can take will now be set forth in detail frequent reference will be taken to the drawings reference numbers will sometimes be utilized to indicate certain parts or locations in the drawings the same reference numbers will be used to indicate the same parts and locations throughout the drawings unless otherwise indicated in this description a single cellular telephone circuit with an add on circuit according to the present invention will be shown however the description will be in the context of course of two way duplexed voice communications between two cellular telephones in a conventional cellular telephone system in this example one phone will be discussed as if it were being used by the reader the other will be used by a second person at a remote location in the cellular network therefore to distinguish between the.