Просто по инерции нарыл в интернете информацию
по HART модемам:
http://www.chip-news.ru/archive/chip...Article_05.pdf
http://www.metran.ru/catalog/ao/ao_13.html
http://www.microflx.com/InLinkModem.htm
http://www.hartcomm.org/hcf/document...ments_opc.html и ещё:
The HT2012 HART ® (Highway
Addressable Remote Transducer) is a
single chip CMOS low power FSK
modem which operates at the Bell 202
standard. It is designed to provide
HART® communication capabilities in
process control instrumentation and
other low power equipment, and provides
a low cost, reliable single chip modem
capability conforming to the HART®
Physical Layer.The HT2012 is designed for use
as a peripheral device to a local
microprocessor or microcontroller. All
interface lines are digital and can directly
connect to CMOS or TTL level
components.
Бьёт на километры по телефонной "лапше".