Patent ID: 6574280
Filing Date: 2003-06-03
Classification: H04L,H04M

Abstract:
A method for initializing a data transmission system having a calling device configured to communicate with an answer device via a digital communication network, said method comprising the steps of:establishing a communication channel between said calling device and said answer device; obtaining a received digital channel identification (DIDc) sequence at said answer device, wherein said received DIDc sequence is associated with a DIDc sequence transmitted by said calling device over said communication channel; analyzing said received DIDc sequence to determine whether said communication channel is a fully digital channel; and entering a full digital mode if said analyzing step determines that said communication channel is fully digital; wherein said DIDc sequence comprises a plurality of pulse code modulation (PCM) codewords, and wherein each of said plurality of PCM codewords is an eight-bit codeword comprising a sign bit such that said DIDc sequence is associated with a plurality of sign bits, said plurality of sign bits are encoded in accordance with a scrambling algorithm, and each of said plurality of PCM codewords is formatted in accordance with a bit pattern S00001{overscore (S)}S, wherein S indicates a scrambled sign bit for each of said plurality of PCM codewords.