Digium's quad span digital interface cards support 96 (T1 / J1) or 120 (E1) connections to PSTN trunks over four spans (digital circuits). Built exclusively for use with Asterisk and Asterisk-based communications systems, the quad span digital cards provide the best value in digital connectivity.Quad span digital cards are available in PCI and PCI-Express form factors. All quad span models can be combined with an Octasic DSP-based echo cancellation module from Digium to provide effective hardware echo cancellation across all channels.Digium cards are compatible with all versions of Asterisk using the DAHDI driver framework. Asterisk and DAHDI are available for free from the Asterisk.org website. All cards include a five (5) year warranty and are eligible for Digium's Exceptional Satisfaction Program (ESP) risk-free Quality Guarantee.