| 摘要 |
A multi-frequency or voice frequency receiver is employed in telecommunication systems to receive and test digital signals from stations having multi-frequency control signalling facilities, and to receive digital information from similarly equipped data transmitting stations. The receiver has a number of tests which it performs on the received signals prior to passing the signals to the translators and decoders. The signals used are the standard eight tone, two group signals which are checked as to frequency, duration, the presence of one tone per group, minimum amplitude level and signal amplitude. In the receiver, the filter networks employ active filtering principles.
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