Nortel Networks DCT1900 - Manual (Page 41)

Technical Product Manual - DCT1900
System Description, Radio Exchange Boards
System-DCT1900/R8/mw 4-3
© 2000-2005
4.4 Speech Processing Unit - SPU-S (REX-BRD0017 or ROFNB 157 16/3)
The SPU interfaces between a LTU/DTU and a CLU/SLU. Every SPU board contains eight Speech
Processing Channels (SPC, see Figure 4-2). Every SPC handles the speech processing for one
call. When a call is initiated, either by a Portable Telephone or by an incoming call, an SPC is
assigned to the call.
The main functions of the board are:
z 64 kbit/s PCM to 32 kbit/s ADPCM transcoding and vice versa
z DTMF generation and dial tone detection
z Echo control
Fig.4-2 SPU
SPC
1
SPC
8
Peripheral
P8
Peripheral
P1
BC