BT8954 CONEXANT [Conexant Systems, Inc], BT8954 Datasheet - Page 11

• Manufacturer Part Number: BT8954
• Description: VOICE PAIR GAIN FRAMER
• Manufacturer: CONEXANT [Conexant Systems, Inc]

N8954DSC
1.0 DSL Systems
1.1 Voice Pair Gain Applications
A well-established market exists for voice pair gain systems. In such systems,
several simultaneous phone conversations are transported over a single twisted
pair. These systems are used by telecommunications service providers to
maximize the utilization of the existing copper plant and allow it to provision
many more telephone circuits than is possible with ordinary 4 kHz analog
transport. The external interfaces of voice pair gain systems, at both the Central
Office and remote ends, are analog POTS lines. Two carrier techniques facilitate
single pair gain transmission: Frequency Domain Multiplexed Systems (FDM)
and Time Domain Multiplexed Systems (TDM). In FDM systems each voice
channel is modulated by a successively higher carrier such that the composite
transmission consists of several frequency bands. In TDM systems the voice data
is digitized and sampled in a channel-multiplexed fashion. Although FDM
systems are currently fielded, recent trends are clearly toward TDM systems
because of the inherent advantages associated with digital transmission.
combination of 2:1 Adaptive Differential Pulse Code Modulation (ADPCM)
compression and basic rate Integrated Service Digital Network (ISDN)
U-interface devices to transport four-voice conversations on one twisted pair. The
disadvantage of this scheme is that clear 64 kbps channel capacity is lost due to
the ADPCM voice compression algorithm. This may prevent high-speed
facsimile and data transmissions from being transported reliably. Since
telecommunication service providers want to provision telephone equipment that
can be used for business purposes, this disadvantage has caused them to seek
alternative solutions that can handle data as well as voice. When used with a
Digital Subscriber Line (DSL) bit pump, such as the Bt8960, PCM4 systems can
be constructed to transmit clear 64 kbps channels, thereby enabling voice, fax,
and data transmission.
greater number of voice conversations to be simultaneously carried over a single
twisted pair. The Bt8954/Bt8970 combination can facilitate up to 18 64-kbps time
slots. If clear channel capability is needed, this combination results in up to
18 (PCM18) systems. When used with 2:1 ADPCM voice compression,
the Bt8954/Bt8970 combination makes up to 36 voice channels possible.
Traditional PCM4 (also called “1+3”) voice pair gain systems use a
The Bt8954 with a higher speed DSL bit pump, such as the Bt8970, allows a
Conexant
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