These cards are sold in seperate modules on our site.
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Digium Wildcard AEX2400 P
The AEX2400P is a full-length P  CI 2.2-compliant card for connecting analog telephones and analog POTS lines through a PC. It supports a combination of up to 6 'Quad FXS' and/or 'Quad FXO' modules for a total of 24 lines.

Using Digium's Asterisk software and standard PC hardware, one can create a telephony environment that includes all of the sophisticated features of a high-end business telephone system.

Using an industry-standard bursting, bus-mastering interface chip that is found within millions of PC systems worldwide, and Digium VoiceBus technology, the AEX2400 eliminates the requirement for separate channel bank and T1 interface cards, with industry-leading performance and price. The quad trunk and quad station modules are interchangeable, allowing the creation of any combination of interfaces. The optional hardware echo cancellation module provides 1024 taps (128 milliseconds) of echo cancellation for superior voice quality on both trunk and station interfaces. Scaling of this solution is accomplished by adding additional AEX2400 interface cards.

FXO/FXS Module Combination Comparrison Guide
Cards Without Echo Annulation Module