Zhone Technologies IMACS Network Device - Manual (Page 71)

Zhone Technologies, Inc. IMACS Product Book, Version 4
March 2001 Page 67
The sum of the compression rates for the engine pair must equal 64Kbps. A 32Kbps circuit can only be paired with
a 32Kbps circuit. A 40Kbps circuit can only be paired with a 24Kbps circuit and vice-versa. The ADPCM server
card can also pair a low speed asynchronous data transmission (19.2Kbps or less) from an SRU port with a 40kbps
engine. This data path will occupy a 24Kbps engine. Group II FAX is supported in 32Kbps channels and Group III
FAX is supported in 40Kbps channels.
Modem support up to 4.8Kbps, and V.32bis to 9.6Kbps is supported in 32Kbps channels. Modem speeds up to
12Kbps, and V.32bis speeds up to 14.4Kbps is supported in 40Kbps channels. Modem data is not supported in
24Kbps channels.
The ADPCM card supports Transition Signaling as defined by ANSI T1.302-1989 with the exception of the Alarm
bits. ANSI T1.302 specifies signaling at the 32Kbps compression rate. The ADPCM card uses this scheme for
24Kbps and 40Kbps although it is not included in the standard.
The ADPCM card can be used in a variety of applications to reduce the number of transmission lines for efficient
transport of voice traffic. It can be used in:
•
PBX-to-PBX trunk application
•
Automatic Call Distribution application
•
Efficient wireless base station/hub application
PBX-to-PBX Trunk Application
Figure 21a shows the IMACS with an ADPCM server is used to compress two T1 or E1 PBX-to-PBX trunks into a
single trunk. The voice from each PBX is connected via a digital T1 or E1 connection to the IMACS. The voice
channels are routed to the ADPCM server, where each voice channel is compressed to 32 Kbps. The compressed
voice is routed to the outbound T1/E1 link to the other IMACS unit, where it is decompressed and placed back into
two T1 or E1 trunks to the remote PBX. PBX-to-PBX trunk lines can be compressed 2:1 to reduce leased line
charges. The application is also valid for analog PBXs and key systems.
PBX
T1/E1
T1/E1
IMACS IMACS
PBX
T1/E1 carrier
Network
Figure 21a - IMACS Using ADPCM for PBX to PBX Application