It sounds like they might be Wiegand outputs.

Try this for a start.
http://www.kerisys.com/pages/download/techdocs/PXL-250W_Wiegand_Data_Format_Reference_Document.pdf

----- Original Message ----- 
From: "jwolfe" <jwolfe@elmore.rr.com>
To: <piclist@mit.edu>
Sent: Saturday, July 22, 2006 15:54
Subject: [PIC] Security Keypad to 16F88


I have acquired two Radio Shack security keypads - one 49-452 and one
49-462.


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