If a DSX panel has been operating in a non-controlled environment for 20+ years, the wire-wrap pins might start to tarnish which could introduce noise into the circuit.  Telect recommends using our DSX panels at a Humidity of 0% to 90% and in a non-condensing environment.  If there is tarnish on the wire-wrap pins, it is possible to clean the wire-wrap pins and re-terminate the wiring.  Once cleaned any noise introduced from a dirty wire-wrap pin should be removed from the circuit.