Here is a spec sheet from '96: http://www.ti.com/lit/ds/slws011d/slws011d.pdf http://www.ti.com/lit/ds/slws011d/slws011d.pdf Back then they used a 40 bit roll

Here is a spec sheet from '96: http://www.ti.com/lit/ds/slws011d/slws011d.pdf http://www.ti.com/lit/ds/slws011d/slws011d.pdf Back then they used a 40 bit rolling code. Found here: http://auto.howstuffworks.com/remote-entry2.htm http://auto.howstuffworks.com/remote-entry2.htm