Invalid or Vacant Code recordings indicate the caller dialed a non-existant area code and/or office code, or possibly some other sequence of digits that the switching equipment can’t handle. These recordings are different than intercept announcements for specific phone numbers that are changed or unassigned. Occasionally though, they were heard in that context. Generally, vacant code recordings were played by toll and tandem switches, while intercept recordings came from the terminating central office.
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