VoIP Gateway TAU-4.IP

Key features
  • Office PBX functionality
  • 3G/4G channel reservation
  • IPsec encryption
  • TR-069/DHCP-based autoprovision
  • Maximum line length—6 km
  • Measurement of subscriber's line parameters

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Physical parameters
Documents and files


TAU-4.IP VoIP gateway is an optimal solution for provision of advanced VoIP services to corporate clients via analogue phone devices.

Business solution
Due to the wide function set, TAU-4.IP can be used as an independent mini office PBX with internal switching and basic set of value added services as well as in interaction with IP PBX.

High-Quality Sound
A high-performance hardware platform support for all popular audio codecs used in VoIP networks (G.711, G.723.1, G.726, G.729), echo cancellation, silence detector, comfort noise generator, DTMF signals reception and generation and traffic prioritization (QoS) ensure the high quality of the voice data.

In case of loss of the main connection to the Internet, there is a possibility of automatic switching to a backup 3G/4G channel. If there is no a backup channel, the connection between gateway subscribers is saved.

Centralized configuration downloading, intellectual firmware update and collection of data on subscriber gateway status can be realized through Eltex.ACS system via TR-069. Eltex.ACS provides simplicity of Eltex CPE management and reduces operating expenses.


  • 4 FXS ports
  • 1 WAN 10/100 Base-T
  • 1 USB port

VoIP protocols

Voice codecs
  • G.711 (a-law, µ-law)
  • G.723.1
  • G. 726 (24 Kbps and 32 Kbps)
  • G.729 (A/B)

Fax transmission
  • T.38 UDP Real-Time Fax
  • G.711 (a-law, µ-law) pass-through

Voice standards
  • VAD (Voice Activity Detector)
  • CNG (Comfort Noise Generation)
  • AEC (Acoustic Echo Cancellation, G.168 recommendation)

Functional features
  • Payphones connection
  • Subscriber line’s physical parameters measurement
  • Local switching in case of a SIP-server connection failure
  • VAS management via a phone
  • Distinctive Ring
  • Keep-alive during operation behind NAT
  • Calling Party Control (CPC)

  • Signal detection and generation
  • Transmission by INBAND, RFC 2833, SIP INFO methods

Supplementary services
  • Call Hold
  • Call Transfer
  • Call Waiting
  • Call forwarding when busy (CFB)
  • Call forwarding on no reply (CFNR)
  • Call forwarding unconditional (CFU)
  • Calling line identification (FSK Type I, FSK Type II, DTMF)
  • Calling Line Identification Restriction (CLIR)
  • Hotline/Warmline
  • Call Group
  • 3-Way Conference
  • Pickup Group
  • Hunt groups
  • A dedicated server for 3-Way Conferencing (RFC 4579)

VoIP functions
  • Local connection switching
  • Operation without a SIP server
  • Flexible dial plan
  • Management profiles for FXS ports
  • SIP profiles (support for up to 8 profiles)
  • Geographical redundancy of a SIP server (up to 4 redundant SIP servers)
  • Application of settings without reboot
  • Voice transmission through a protected channel (encryption through Ipsec)
  • IMS (3GPP TS 24.623) for Call Hold, Call Waiting, 3-Way Conference, Hotline management
  • Using SIP servers from DHCP-option 120
  • Support for operation behind NAT (STUN and Public IP)
  • Setting custom call-control signals

Quality of service (QoS)
  • DSCP and 802.1p assignment for SIP and RTP packets
  • Bandwidth redundancy

Network functions
  • Different protocols for connection to a service provider network (Static, DHCP, PPPoE, PPTP, L2TP)
  • Local DNS server
  • Static and dynamic routing
  • VLAN per service (VLAN for each service: Internet, VoIP, Management)
  • Firewall
  • Operation via 3G/4G USB modems with connection redundancy
  • Print server
  • IPsec (for voice transmission and remote control)

  • Web interface (multilingual*)
  • SNMP (phone parameters configuration, monitoring and statistics gathering)
  • Telnet
  • Syslog
  • Tcpdump
  • SSH
  • TR-069 (Eltex.ACS server is recommended)
  • DHCP-based autoprovisioning (43, 66, 67 DHCP options)
  • Management via IPsec encrypted channel

  • Username and password authentication
  • Firewall
  • Access rights differentiation for admin/user
  • Password encryption
  • Digest authorization

USB port
  • USB storage connection with FAT/FAT32/EXT2/EXT3/NTFS file systems — file exchange according to FTP protocol
  • USB 3G/4G modems connection — 3G/4G channels redundancy
  • Printer connection — setting up a print server

Technical features
  • SDRAM 256 MB
  • Flash 32 MB
  • OS Linux

  • RFC 3261 SIP 2.0
  • RFC 3262 SIP PRACK
  • RFC 4566 Session Description Protocol (SDP)
  • RFC 3263 Locating SIP servers for DNS lookup SRV and A records
  • RFC 3264 SDP Offer/Answer Model
  • RFC 3311 SIP Update
  • RFC 3515 SIP REFER
  • RFC 3891 SIP Replaces Header
  • RFC 3892 SIP Referred-By Mechanism
  • RFC 4028 SIP Session Timer
  • RFC 2976 SIP INFO Method
  • RFC 2833 RTP Payload for DTMF Digits, Flash event
  • RFC 3108 Attributes ecan and silenceSupp in SDP
  • RFC 4579 SIP Call Control - Conferencing for User Agents
  • RFC 3361 DHCP Option 120
  • RFC 3550 RTP A Transport Protocol for Real-Time Applications

*Supported in the firmware version 1.2.1 and higher

Physical parameters

Power adapter
  • 12 V DC, 2A
Power consumption
  • up to 11 W
Operating temperature
  • from +5°С to +40°С
Operating humidity
  • up to 80%
  • 218х49х120 mm, desktop case
  • no more than 0.3 kg

Documents and files


Regardless of the operational lifetime stage, Eltex provides a 12 months warranty on all its telecommunication equipment.

During the warranty period the manufacturer ensures technical support and free-of-charge repair at the Enterprise which is situated in Novosibirsk.

As part of the warranty service, technical support is provided on the first-in first-out principle.

The priority support packages of 8/5 and 27/7 types are subjects to additional charges.