Legacy Telecom

fax, modem, Iwf and VoIP gateway


We know that the uptake of next-gen technologies can be slow – particularly on the enterprise front. Consequently, fax is still used for legal communications, modems are preferred for remote financial services, and telecom operators are still required to provide cross-platform connectivity between fixed and mobile networks and users.

Overcoming these legacy inter-operability / bridging challenges becomes a key element when evaluating the upgrade of an existing core-infrastructure, and therefore constitutes a strategic component of SURF’s solution arsenal.



High Density Blades

240 modem ports and up to 800 fax ports per blade

All Modem Protocols

From low bitrate V.21@300 bps, to V.90 with up to 56Kbits / second

Software Library

Fax functionality available as a software library that runs on any COTS IA server


Scalable Blades / Software

Can be supplied in a partially populated form to address smaller installations or sotware only for NFV migrations

TDM Bearer Channel Interface

IWF accommodates native TDM interconnectivity, or over an IP/UDP/RTP transport (RFC4040) for LTE core


  • SURF’s IWF 3G → PSTN/ISDN interworking function for circuit switched fax and data solution is utilized and deployed by all leading mobile infrastructure TEM’s.
  • SURF’s FAX server solution and FoIP gateway technology have been commercially available for over 16 years, marking an unprecedented and unrivalled interoperability record.
  • SURF is the largest supplier of MODEM ports, with tens of millions of deployed ports.
  • SURF provides a software echo canceller for migration to NFV networks.
  • All these solutions are offered either as an integrated hardware+ software solution, or as a software license that can be integrated on to the TEM’s existing hardware infrastructure.


Fax Table

Modem Pool


SURF Blades

Learn More About SURF's Legacy Telecom Solutions

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