| 摘要 |
A system and method are disclosed for preventing intelligible interception of information signals transmitted over a two-direction line. A masking signal is applied through a hybrid circuit at the receiving end of the line, and this masking signal, which appears on the line together with the information signal, prevents intelligible decoding. Only at the receiving end of the line, where the hybrid circuit attenuates the masking signal which it receives at its receive port, can intelligible decoding take place. Signal processing techniques used at the receiving end permit larger amplitude masking signals to be used, thus creating even greater confusion for an unauthorized detecting mechanism which is coupled to the line. |
