Digital Line Interfaces


Sirrix.PCI ISDN is a family of PCI-based ISDN interface cards. They provide either basic rate interface (BRI, S0) ports or primary rate interface (PRI E1, S2M) ports depending on the model. These ports can be connected either to the public network or internally to PBX systems or other ISDN devices. The cards are fully ISDN compatible and can be employed for voice applications as well as for data communications.

Hardware structure

The BRI ports are provided by Infineon PSB 21150 (IPAC-X) interface circuits and the PRI ports by Infineon PEF2256H (FALC56) interface circuits. Communications with the software is realized by an FPGA using the PCI bus.

The optionally available crypto mechanisms are realized in hardware and included within the FPGA. They allow zero-delay encryption and decryption of the B channels.

Port configuration

All BRI lines can be configured independently to work in the network termination (NT) mode or terminal equipment (TE) mode. In both modes, they can be operated as point-to-multipoint (PTMP) or as point-to-point (PTP). Each E1 port is independently configurable in NT (clock master) and TE (clock slave) mode.

Integrated PCM bus

All cards in the Sirrix.PCI ISDN family offer a high-speed internal PCM bus, making it possible to interconnect any variation of Sirrix.PCI ISDN cards within one fully featured hardware-based ISDN PBX. This provides perfect quality voice and data transmission with zero delay.

Hardware echo cancellation

The onboard Octasic DSP echo cancellation module performs voice quality enhancement (VQE) functions for up to 64 channels.

Conference bridge

The cards include a hardware conference bridge featuring arbitrarily sized conference rooms with optimized noise reduction and level control. Sirrix.PCI ISDN cards ensure effective communications and a pleasant call experience.

Optical display

The activation of the ports are indicated by 4 LEDs on the rear bracket. There are 2 more internal LEDs indicating the overall status of the card and its FPGA.

ISDN facilities support

Almost all ISDN facilities are supported by Sirrix.PCI ISDN cards. This includes calling line identification presentation (CLIP ), call forwarding (CF), call waiting (CW), call hold and transfer, advice of charge (AOC) and AOC during call (AOCD), etc. In addition, Sirrix.PCI ISDN cards support direct dial-in (DDI) and multiple subscriber number (MSN). Certain Q.SIG supplementary services are implemented as well to improve the interworking with PBX systems. Calling name identification presentation CNIP) and connected name identification presentation (CONP) provide the most valuable features, allowing to names to be presented instead of numbers.

TETRA support

The E1 models of the Sirrix.PCI ISDN cards also support operation in a terrestrial trunked radio (TETRA) environment. Control rooms can be connected via these cards acting in a gateway to TETRA exchanges. In this application, the E1 ports provide eight TETRA voice channels of 8 kb/s each on all 31 bearer channels of 64 kb/s each. Thus 248 TETRA coded voice channels are supported simultaneously per E1 port. All those channels can be freely mixed in any combination of individual and group calls.

Possible applications

Sirrix.PCI ISDN cards can be used, e.g. with the open-source PBX Asterisk software for which a channel driver is provided. With Sirrix.PCI ISDN cards, everyone can build flexible, PC-based PBX systems that allow many more capabilities than off-the-shelf  PBX. In addition, the cards can be used to build ISDN crypto gateways, voice-over-IP gateways or least-cost routers.


Sirrix.PCI ISDN cards can be operated in an arbitrary PCI-based system with 32-bit PCI 2.1 and Linux kernel 2.6.