Default codec for POTS is g.711
Default codec for VOIP is g.729
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucme/admin/configuration/manual/cmead m/cmebasic.html#concept_2A67E83FAC004CF5AC02FCFF49FCE6BB

A voice translation rule on a Cisco voice gateway uses regular expressions (regex) to match and modify numbers. To truncate a number down to its last four digits, the regex pattern must match the entire number and capture only the last four digits for replacement.
rule 1 /^.*\(...\)/ /\1/
- ^.*: Matches any leading digits before the last four digits.
- \(...\): Captures the last four digits in parentheses. The parentheses create a capture group.
- /\1/: Replaces the entire number with the content of the first capture group (the last four digits).