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SIP Analog Modem Server for Facsimile (SAMS-F)


The VOCAL SAMS for Facsimile (SAMS-F) is a solution for interoperating with legacy fax modems without the need for modem banks with E1/T1/ISDN connections.

As E1/T1/ISDN lines are increasingly being replaced by Ethernet based VoIP systems, companies are often left with modem based technology that can no longer work with the new infrastructure. This however is unacceptable for many businesses where FAX documents remain critical for operations. VOCAL has a number of solutions to solve these problems.

VOCAL’s Virtual Modem Servers allows a business to deploy a server in the cloud, which can work with the modern VoIP phone network infrastructure, based on SIP and RTP, instead of necessitating T1/E1/ISDN lines to connect to the PSTN. The VOCAL Virtual Modem server contains true soft-modems, not just an AT command set on a TCP socket, pretending to be a modem. This allows the server to connect to true voice-band fax machines and fax modems deployed on the PSTN, and thus does not require installation of additional equipment on the far end of the system. The server is controlled by industry standard AT FAX commands via standard TTY nodes in the server’s filesystem – just as if it were a box-modem on a serial connection. This allows it to easily fit into currently existing systems. Many other configurations and methods of control are available in order to flexibly meet the needs of already deployed infrastructure and applications. In addition, VOCAL can customize or build to suit, in order to meet very specific system requirements.

Fax over IP (FoIP) solutions, can work in a few ways. They can treat fax modem audio signals as simple data, which may be packetized and transmitted in real-time over IP networks. Audio tones are sampled and digitized at (or near) the source, the data packets are transmitted over IP networks using VoIP protocols, and demodulated at the destination. As such, Fax over IP eliminates POTS lines and associated expenses. However it does not eliminate the use of the encoding and decoding modem audio at the source and destination nor the modem banks at the ISP. This allows for compatibility with existing Fax machines.

FoIP solutions can also work by directly sending T.38 FoIP data directly to IP network, without modulating the data on the IP end. The telephone network utilizes T.38 gateways, with which the FoIP endpoint can communicate. The T.38 gateway in the network will modulate the data and send it to the far end endpoint, which again can be already existing, standard Fax machines.

The SAMS-F Software is part of a fully integrated and highly configurable VoIP software solution with a Network Stack, SIP Stack, secure communications, full-featured Telephony software, and a comprehensive fax protocol and fax modem software library.


  • 100% software solution easily migrates to the cloud
  • Runs on any standard Linux or Windows Server distribution
  • Replaces RAS equipment configurations when analog lines are being replaced with VoIP (SIP/RTP) lines
  • Scalable – enables a large number of modems on a single server (10s to 100s depending on the server and modem rates)
  • Exports TTY (or com port) interface for each fax modem
  • Registers with one or more SIP servers (can be phone number per line, modem pool hunt, or other combinations)
  • SRTP and Secure SIP options available
  • Dialing commands will make outgoing SIP/G.711 call (with modulation data in the stream)
  • Incoming SIP calls will report RING to applications listening to TTYs
  • Requires no analog audio interface
  • Slaves to far end modem clock to eliminate skew
  • SIP-based system available for industry standard and proprietary Fax over IP networks
  • Direct interface to 8.0 kHz PCM RTP data stream (A-law or μ-law)
  • Group 3 Facsimile direct T.38 protocol interface
  • Fully integrated Group 3 Facsimile processing system
  • Facsimile service class 1, 2.0, 2.1 command sets (T.32, EIA-592 and industry standard fax class 2) available.
  • Fully compliant with ITU Recommendations
  • T.30 Fax Protocol (session control and negotiation)
  • T.30 Error Correction Mode (ECM)
  • T.4 1-dimensional Fax Image Decoding/Reencoding (MH)
  • T.4 2-dimensional (MR) / T.6 Fax Image Decoding/Reencoding available (MMR)
  • Configurable type/amount of redundant information for UDP/IP service
  • Configurable to support UDPTL forward error correction messages
  • Configurable high speed training mechanism – Local TCF generation or TCF transmitted between end-terminals

Fax Modulations

  • V.34 fax – 2400 to 33,600 bps
  • V.33 – 12000 and 14400 bps
  • V.29 – 7200 and 9600 bps
  • V.27ter – 2400 and 4800 bps
  • V.21 Channel 2 – 300 bps FSK
  • V.17 – 7200, 9600, 12,000 and 14,400 bps

More Information

supported platforms

VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202
Amherst New York 14228
Phone: +1-716-688-4675
Fax: +1-716-639-0713