| 摘要 |
A supervisory signal for a derived channel data reporting system is implemented as a tone having a frequency capable of transmission using a telephone signal communicating network, including networks incorporating digital equipment, at an attenuated level. The tone preferably has a frequency of from 200 Hz to 300 Hz, and is capable of operating in conjunction with biphase modulated (BPSK), frequency shift keyed (FSK) and multi-tone modulated (MLT) polling systems. Such frequencies are effectively communicated by conventional digital loop carrier systems, despite a limited frequency range, and are of a sufficient magnitude to be detected by the derived channel data reporting system. |
