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  2. Call screening - Wikipedia

    en.wikipedia.org/wiki/Call_screening

    Call screening is the process of evaluating the characteristics of a telephone call before deciding how or whether to answer it. [1] Some methods may include: listening to the message being recorded on an answering machine or voice mail. [1] checking a caller ID display to see who or where the call is from. [1]

  3. Vertical service code - Wikipedia

    en.wikipedia.org/wiki/Vertical_service_code

    As CLASS was an AT&T trademark, the term vertical service code was adopted by the North American Numbering Plan Administration. The use of vertical is a somewhat dated reference to older switching methods and the fact that these services can only be accessed by a telephone subscriber, going up ( vertically ) inside the local central office ...

  4. Room 641A - Wikipedia

    en.wikipedia.org/wiki/Room_641A

    Room 641A is a telecommunication interception facility operated by AT&T for the U.S. National Security Agency, as part of its warrantless surveillance program as authorized by the Patriot Act. The facility commenced operations in 2003 and its purpose was publicly revealed by AT&T technician Mark Klein in 2006. [1] [2]

  5. Enhanced 911 - Wikipedia

    en.wikipedia.org/wiki/Enhanced_911

    Basic 911: All 911 calls must be relayed to a call center, regardless of whether or not the mobile phone user is already a customer of the network being used. [13] E911 Phase 1: Wireless network operators must identify the phone number and cell phone tower used by callers, within six minutes of a request by a PSAP. E911 Phase 2:

  6. Mobile Telephone Switching Office - Wikipedia

    en.wikipedia.org/wiki/Mobile_Telephone_Switching...

    When the MSC gets the call, it checks its database for the location of the phone. Then it picks a frequency pair the phone will use in that cell to take the call. The MSC communicates with the phone over the control channel to tell it which frequencies to use, and once the phone and the tower switch on those frequencies, the call is connected.

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  8. Blue box - Wikipedia

    en.wikipedia.org/wiki/Blue_box

    To reduce call set up time, telephone numbers were transmitted from machine to machine in a "speed dial" format, about 1.5 seconds for a 10-digit number, including KP and ST. To catch the cheaters, AT&T could have connected monitors to digit receivers that were not being used for operator dialed calls and logged calls dialed at manual speed.

  9. 1-800-COLLECT - Wikipedia

    en.wikipedia.org/wiki/1-800-COLLECT

    Prior to 1993, collect calling was a virtual monopoly held by AT&T as people were accustomed to dialing "0" to place collect calls. MCI moved aggressively to insert itself into the market by launching 1-800-COLLECT that year.