Loop current, circuit loss, or imbalanced line can cause caller ID problems on a POTS line. Take a Sidekick T & N and test for load coils. Load coils are generally added to long loops to extend the range of telephone service and need to be properly spaced for correct operation of Caller ID. Signs to look for: excessively Low volume(customer can't hear), excessively high volume, hum in line. Loop current should ideally be between 23ma to 35ma and circuit loss ideally around -5.5db, when calling the 1KC Tone from the LOCAL co.
