John,  try  www.microchip.com    microid section. download the rfid system
design design guide. 125khz seems to be the main frequency but I think the
134.8khz systems work the same.
Also a quick web search came up with


[DOC] Subject:
File Format: Microsoft Word 97 for Macintosh - View as HTML
... 64. »-42. ISO 18000-2. 125/134.2 kHz. fc ± 4 ... of the Band
135.7-137.8 kHz by
the Amateur Service. - CISPR ... integrated circuit(s) cards - Proximity
cards -. ...
www.ero.dk/EROWEB/Public%20consult-October01/SE_Draft_ECC_Report01.doc -


Good luck

Sandy

WB5MMB