The noise on a telephone line is the result of many things. The main source of noise is the electrical interference from other devices on the same line. This can be caused by appliances such as refrigerators, air conditioners, and computers. Other sources of noise include static from the line itself and from the electrical … Read more


The term “2600” is a common name for the monthly magazine published by the International Organization for Standardization (ISO). The magazine is named after the ISO’s standard numbering system, which is used to designate international standards. The magazine covers a wide range of topics, including standards development, certification, and conformity assessment. It also features articles … Read more

Direct Inward Dialing (DID)

Direct Inward Dialing (DID) is a telephone service feature that allows callers to directly reach a specific extension on a private branch exchange (PBX) system without having to go through a PBX operator. DID numbers are assigned to specific extensions on a PBX system, and are typically advertised to the public as a way for … Read more


A ringback is a signal that is transmitted to the calling party by the called party’s telephone exchange to indicate that the called party’s telephone is ringing. How do you use ringback? A ringback is a signaling tone that is heard by the calling party when the called party’s line is busy. The tone indicates … Read more