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The CCITT specify the standards for the layers 1, 2 and 3 signalling messages. Layer 3 messages are the messages which actually control the call setup, teardown, and routing. The layer 3 messages or call control messages are the minimum messages that must be understood by the interfacing equipment. Individual service providers may publish their ...
To its mobile telephone business customers BT Group provides a 1571 Voicemail service, which is similar to the service provided to landlines. Calling parties can leave messages when the mobile telephone is switched off, when it is in an area of reduced coverage, when it is on another call, or when the call is not answered within a fixed number of rings.
When dialling within the same area, the area code is not needed, save for a handful of areas that do require this. When calling from a mobile telephone or through a VoIP service, such as BT's 'Digital Voice', the area code is always needed.
Used to set up and control speech and data calls between Bluetooth devices. The protocol is based on the ITU-T standard Q.931, with the provisions of Annex D applied, making only the minimum changes necessary for Bluetooth. TCS is used by the intercom (ICP) and cordless telephony (CTP) profiles. The telephone control protocol specification is ...
The first subscriber's phone (called the 'audio customer') would be connected as normal. The second subscriber (called the 'carrier customer') would have his phone calls modulated on to an RF carrier or Carrier wave on the same physical phone line at around 40 kHz – high enough not to be noticeable to the audio customer.
The Post Office/BT system is described here from the original term ‘Engineering Circuit Designation’. Other PTOs have their own scheme and would be suitable for inclusion. The Post Office or BT system historically used PW and R, optionally followed by a Region and/or Area code, followed by a number of digits between 4 and 6 for rented ...
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Enough bandwidth is retained for voice telephony and the majority is used for high speed data. All phones (or other voice band devices) must be connected via a filter (either a separate filter for each phone or one filter covering multiple phones) to avoid interference between the phones and the DSL signal.