A novel timing-delay measuring method based on PN code in telephone time service

The key problem of telephone time service by PSTN is how to synchronize user time with standard time, in other words, measuring time delay of transmission is the important problem. Now, there are two methods of measuring time delay, the first way is by transmitting character signal; the second way is through phase-detecting. The precision of measuring time delay will have a directly influence on system synchronization time precision, also, The traditional analog modulation/demodulation will highly effect the precision, but the phase error is inevitably because of the effect caused by the noise and channel characteristic when using phase-detecting. A new method, using correlation of PN code will be presented in this paper. Testing shows it can obviously improve the precision of telephone timing service.