Here is Pennsylvania's take on the matter

*57 or Appropriate Call Trace Code. A call trace feature offered by the Commonwealth's telecommunication carrier which can be activated by pressing a designated code. The feature code locks the last incoming call in storage. The information is only accessible by the responsible law enforcement agency. Most locations provisioned as Type 1 and 2 lines from TelCove utilize the *57 feature code; however, Type 5 lines (re-billed lines from Independent Vendors) are handled differently according to each Vendor.

(1) Lines located in Sprint territory carry the *57 call trace capability on all lines. However, they will not report a trace to the authorities until 3 successful traces have been made.

(2) Lines located in Commonwealth Telephone Company and Northeastern Telephone territory, as
well as Business Lines in Verizon territory automatically carry the *57 call trace feature. However, Centrex lines in those territories may have different codes and agencies should refer to the list on the OA/BIO website listed below.
NOTE: Some rural areas and old PBX systems may not be equipped to handle the Call Trace feature.

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