Digital Module SFP-E1 for Asterisk

E1 digital telephone module in SFP form factor for integrating IP-PBX Asterisk with PSTN or legacy PBX


  • Integration with Legacy PBX, Asterisk IP-PBX, IVR Services
  • VoIP Gateways (supports SIP, H.323 and IAX)
  • SyncPPP, Frame Relay, Cisco HDLC, Multi-link PPP
  • a-Law, μ-Law, and Linear Modes Supported
  • Line coding HDB3, AMI


Terratel SFP-E1 module is designed to integrate and connect IP-PBX, IVR systems, VoIP-gateways, other specialized solutions of the Asterisk project or FreeSwitch to office PBXs, as well as the public telephone network PSTN via the E1 interface.

SFP-E1 is an digital module with an SFP form factor (Small Form-factor Pluggable) and support for Ethernet and E1 interface connections.

Digital SFP-E1 module for Asterisk network diagram

Pic 1. Block diagram of the inclusion of a Digital SFP-E1 module for Asterisk.

Digital SFP-E1 module is designed to build digital telephony systems based on Asterisk IP-PBX and exchanges data/voice over E1 channels.

Distinctive features

New SFP-E1 module is the latest addition to the D-201E/D-401E family of digital telephone cards for telephone systems based on open source projects Asterisk and FreePBX.

SFP-E1 module uses unique technologies to support an interface compatible with the Asterisk platform. The SFP-E1 digital module is designed to connect traditional TDM systems with voice over IP technologies in a single telecommunications network.

SFP-E1 module is installed in the sfp-slot of network equipment, which allows it to be used in any place where the network is available, and not just at the location of the Asterisk server.

This is the best solution for allowing Asterisk IP-PBX to connect to PSTN trunks or legacy PBX with E1 interface.

Key Features

  • Up to 30 simultaneous calls per 1E1 port
  • Supports E1 (ITU-T G.703) physical interface connections
  • TDM protocols support: ISDN PRI, SS7, R2 MFC
  • Industry standard RJ-45 port
  • SFP form factor

Connection to the Asterisk telephone system

SFP-E1 digital module is compatible with all Asterisk versions and connects to Asterisk using a special DAHDI-enabled driver. A special driver with DAHDI support is available for free on the website.

SFP-E1 digital module has the ability to configure via the web interface. follow>>

PSTN and SIP trunking

Digital telephone module SFP-E1 by Terratel support 30 (E1 interface) connections to PSTN trunks or legacy PBX over one spans.

SFP-E1 digital module is compatible with the Asterisk system through the DAHDI interface and can support the following protocols:

  • ISDN PRI (Lib PRI)
  • SS7 (Lib SS7)
  • R2 MFC (Lib OpenR2)

Toward an IP network, the Asterisk telephone system supports SIP.

SFP-E1 module has a hardware echo cancellation function for all voice channels of the E1 stream.

How to configure SFP-E1 Digital Module for Asterisk

The device is designed to transmit digital stream E1 over an Ethernet network.

For connection to IP-PBX Asterisk the DAHDI interface is used.

A simplified list of steps required to integrate an SFP device into an Asterisk system:

  • Download the driver assembly from our ftp server
  • Compile and download the driver module for your Linux kernel version
  • Generate a configuration file for the DAHDI system (dahdi_span_assignments dumpconfig> /etc/dahdi/assigned-spans.conf)
  • Configure Asterisk to use regular DAHDI channels
  • Configure SFP module
  • Restart the Asterisk server

Connecting SFP-E1 module via Gigabit Ethernet media converter

If during the installation of the SFP-E1 module there is no physical possibility of its inclusion in the local area network (LAN) through the SFP slot, you must use a budget media converter.

Connecting SFP-E1 module via Gigabite Ethernet Media Gateway

Pic 2. Sample of connecting SFP-E1 module via Ethernet media converter

Gigabit Ethernet media converter is a budget device that is designed to convert the signal and then connect the 1000BASE-SX fiber optic cable with a 1000 Base-T twisted pair cable.

Digital Module SFP-E1 for Asterisk Technical Specifications

System Type
SFP module
Legacy PBX/IVR Services
Voice over Internet Protocol (VoIP) services
Complex IVR Trees
“Meet-Me” Bridge Conferencing
VoIP Gateways (supports SIP, H.323 and IAX)
Calling Card Platforms
Voice/Data Router
PRI Switch Compatibility – Network or CPE
Asterisk IP-PBX
Port Features
HDB3, AMI Line coding
CRC-4, not CRC-4, E1 Frame alignment
Data Transfer Protocols
Frame Relay
Cisco HDLC
Multi-link PPP
Voice Transfer Protocols
E&M Wink
a-Law and Linear Modes Supported
Hardware Requirements
SFP Slot
Software Requirements
Linux kernel 2.6.x