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VoIP subscriber gateways  11 
2.4 Architecture and the device operation principle 
TAU-8.IP/TAU-8.IP-W subscriber terminal consist of the following subsystem: 
–  Controller includes: 
  Mindspeed digital signal processor; 
  flash memory – 16MВ; 
  SDRAM Operating storage – 256МВ; 
–  SLIC Subscriber complex (8×FXS ports); 
–  Ethernet-module RJ-45 10/100/1000BASE-T WAN; 
–  Wi-Fi adapter (only for TAU-8.IP-W); 
–  USB-module. 
Fig. 2 shows the device architecture diagram.  
 
Fig. 2 – TAU-8.IP architecture diagram  
TAU-8.IP architecture diagram differs by absence of Wi-Fi module. 
Linux  operating  system  controls  the  device  operation.  Basic  control  functions  are  performed  by 
Mindspeed  digital  signal  processor  which  enables  IP-packets  routing,  IP-telephony  operation,  group  traffic 
proxying and etc.  
The device can be divided into 4 blocks by functionality:  
–  Device network features block; 
–  VoIP block; 
–  Processing block of multicast traffic; 
–  Control block (Linux operation system). 
Device network features block provides passing and switching IP-packets in accordance with the device 
routing table and can process both untagged and tagged packets depending on network interface settings. The 
block supports DHCP, PPPoE and PPTP protocols. 
VoIP  block  provides  the  device  operation  via  SIP  protocol  to  transmit  voice  signal  through  packet-
switched  network.  Subscriber’s  voice  signal  is  transmitted  to  the  SLIC  subscriber  line  module  to  be  digitized.