A filter passing only desired frequencies is selected according to a desired level of service for copper lines. At a point of access between a loop plant and Central Office, the filter is interposed in series over a telephone service line to provide spectral containment by restricting the frequencies of transmission passing along the line. The filter is preferably mounted within a 5-pin module used in a protector block at the Central Office or remote terminal facility, interfaces with a 5-pin module, or is placed upstream or downstream of a protector block such that it does not interfere with the operation thereof. Service is activated, and the spectral containment apparatus prevents the transmission of unexpected or unintended services over the line.