Understanding will come with knowing the nature of the protocol. Here are some informative documents at currently active web links:

http://www.mercury-security.com/technolog...henyou.htm

http://www.zhlab.cn/technique/T0000006.htm

http://www.hidglobal.com/documents..._wp_en.pdf

Notes to consider if you are intending to use this format...

You may want to design your algorithm to be able to decode the bit pattern based on the relative timing between the pulses on the DATA0 and DATA1 lines and not expect any fixed bit rate.

After you get the bits read in from one code stream transfer make sure to apply the checking of the parity bits to "validate" the transfer.

Be aware that this coding system could be considered to be of a low security nature.

Michael Karas