Assertion: supervision signal | /r/CapableOf | necessitate notch filter
Facets:
value: to prevent interference
type: PURPOSE
Source sentences:
text: In the middle 20th century, supervision signals on long-distance trunks in North America were primarily inband, for example at 2600 Hz, necessitating a notch filter to prevent interference.
text: In the middle 20th century, supervision signals on long-distance trunks in North America were primarily inband, for example at 2600 Hz, necessitating a notch filter to prevent interference.