RLyon,
Correct, and I guess I should correct my previous statement for edification purposes.
Our technicians call it CNG times, but technically that is incorrect. The tones you will hear are actually the FSK tones; Frequency Shift Keying. It sounds similar to a fax or modem synchronization packets, but it has a definite pattern to it.
The CNG tone is a single frequency tone a fax sends out periodically while waiting for another fax to respond with its CED tone. Of course older manual fax machines may not even transmit the CNG tone.
Thanks,
TE
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