ATIS 0600421.2001(S2015)

This standard presents the electrical and physical characteristics of an In-Line filter (initially, and sometimes still, called a micro-filter), that is used to protect voiceband premises equipment from the high frequencies of digital data over voice services in the 25 kHz to 12 MHz range. It is also used to protect data over voice services from impedance changes and other detrimental impairments caused by voiceband equipment. Applications such as alarm systems and series stacking are beyond the scope of this standard.