Telecommunications engineers debugging Bell System infrastructure in the 1980s encountered a documented anomaly: a Dallas-area circuit that showed simultaneous incoming and outgoing calls on the same line without line splitting or multiplexing technology. Technical memoranda from Southwest Bell dated March 1982 reference "Call loop paradox—Fort Worth exchange, subscriber CC Norris." The issue was classified as hardware malfunction and the line was rewired.

Thirty years later, a retired senior technician named Patricia Zhou wrote a memoir about career mysteries. She described the paradox as "the closest I came to understanding something impossible," noting that the subscriber himself seemed unsurprised by the situation. No explanation was ever documented in official records. Modern network engineers occasionally invoke the case when discussing edge cases that defy standard model assumptions.