About this trail:
see Wikipedia's PBX page
Trail link: http://www.trailfire.com/WramblinReck/trails/54606
Summary: http://www.trailfire.com/WramblinReck/trailview/54606
Summary: http://www.trailfire.com/WramblinReck/trailview/54606
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a summary of G.711 A-law encoding:
a single value of the audio sample (a signed, 13-bit, linear number) is converted to an 8-bit floating-point number. (The convention for describing the indexes of the bits in these numbers is big-endian, per the ITU.)
The mu-law encoding of G.711
a single value of the audio sample (a signed, 13-bit, linear number) is converted to an 8-bit floating-point number. (The convention for describing the indexes of the bits in these numbers is big-endian, per the ITU.)
The mu-law encoding of G.711
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See also the TIA/EIA 568A and 568B color codes used in Ethernet Category 5 cabling.
See where "tip and ring" came from (referred to at bottom of this page).
See where "tip and ring" came from (referred to at bottom of this page).
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Federal Standard 1037C: Glossary of Telecommunications Terms
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The demarc is basically the physical point at which the public network of a telco (i.e., a phone or cable company) ends and the private network of a customer begins (e.g., at an office/store/warehouse,etc.)
a concise definition of the demarc here
demarcation point (on Wikipedia)
a concise definition of the demarc here
demarcation point (on Wikipedia)
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T1 is a high speed digital network (1.544 mbps) developed by AT&T in 1957 and implemented in the early 1960's to support long-haul pulse-code modulation (PCM) voice transmission. The primary innovation of T1 was to introduce "digitized" voice and to create a network fully capable of digitally representing what was up until then, a fully analog telephone system.
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A smart jack is a network interface device that terminates a digital circuit, typically a T1 network connection at a demarc (per Wikipedia).
formally known as a continuity check transponder
an interesting newsgroup discussion on smart jacks
formally known as a continuity check transponder
an interesting newsgroup discussion on smart jacks
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A Gatekeeper is sometimes referred to as a Session Border Controller. See also Understanding Gatekeepers by Cisco.
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Fix / Solution:
Configure the IP side of the connection to use a DTMF digit payload type of 101 instead of the value currently being used.
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26 [VoIP ] Prot a=rtpmap:127 telephone-event/8000
The value in question here can be seen on line 26 of the Invite above. The value being requested is 127. This value is a reserved payload type used internally within the gateways DSP firmware and therefore is not available for use with external devices.
Workaround:
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In a SIP telephony integration, touch tones (DTMF) can be passed using RTP . (Note RTP carries voices and other sounds on a phone call setup with SIP.) See here for a good description.
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dual-tone muti frequency - aka "touch tones"
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4 major parts of LAN comm. system:
H.323Zone ≡ one gatekeeper + all terminals, gateways, and MCUs registered to it
H.323Zone ≡ one gatekeeper + all terminals, gateways, and MCUs registered to it
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Skinny IP phones (soft or hard) use SCCP to connect to CISCO CallManager.
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useful in PCM CODECs
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Explains the translation in SIP between SIP URI (which look like FQDNs, sometimes with a phone number as a hostname) and E.164 numbers (phone numbers, as on a PSTN)
See also this .pdf
See also this .pdf
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two 64 kbps bearer channels (carries the payload: voice, data, etc.)
one 16 kbps data channel (carries the signaling info)
one 16 kbps data channel (carries the signaling info)
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