I am a modem professional. I have been in
data communications for over 20 years with major
focus on dial-up and Telco interfacing. I
was with Racal-Vadic for over 14 years and
Ven-Tel Inc. over 5 years. Both were
pioneers in dial-up and leased-line modems.
I have worked in all levels of modems from
product definition, development planning to
sales and management.
If you are trying to decide to make or buy a
modem, select the chipset, questions in layout,
have questions regarding certifications, or
simply need general direction suggestions, I am
available to help you.
It's very confusing trying to decide the best
modem for the application, and then the most
cost efficient direction. There are many
technical issues to resolve before a design
commences… Here are a few:
§
Do I really need 56Kbps or will
33.6Kbps work in my application?
o
What is the difference between
V.92, V.90, V.34, V.32, V.32bis and even lower
speeds?
o
What are the benefits or
liabilities of these speeds?
o
Which has the fastest negotiation?
§
Should I hunt down a 2400?.. a
9600? or maybe a 14.4 is better for my needs?
o
What are the benefits/liabilities
of these speeds
§
Whose chipset to consider?
o
Should I consider ZiLog, Clare,
AMD, TI, Agere(Lucent), SiLabs or maybe
Conexant (Rockwell) – Are there others? -
Can/should I make my own?
o
Which modem company/chipset will
last for my product cycle?
o
What should I do if the
modem/chipset I'm using is EOL'd - (yikes! -and-
HELP!!!)
o
Are there alternates for the final
decision?
o
Are there backup options to
protect my final design?
§
Do I need to monitor or control
all the I/O on a serial interface?
o
What are the minimum I/O signals I
'really' need to monitor or control?
o
How do I manage flow controls?
-
§
What are the advantages of
"inband" vs. "out of band" flow control?
§
What the heck
is flow control anyway and why is it important?
§
What is auto baud and auto
parity? –
o
Are they important? Do I need
them?... Why would I need them?
§
Do I need data compression or
error correction?
o
Does it make a difference?
§
What is the appropriate setup
string for my application?
o
What the heck is a ‘setup string’?
§
Should I consider parallel or
serial interface?
o
TTL, RS232, USB? ...or is there
another?
o
What about I/O voltage/load
compatibility?
§
Do I have a power problem?
o
What are the considerations for
power efficiency of the chipset/or module
available?
o
Should I look at 3.3V or 5V? - Are
there others?
o
Are there performance issues with
the different voltages?
o
Is there an efficient way
to get to "0" power??? (Yes, there is!...)
o
Hmmm, can I run a modem on
telephone line power?
§
Should a "Soft Modem" fit into my plans?
§
Are there patent issues with any modem decision?
o
How do I protect myself
§
What are the FCC/DOC certification issues with
connecting to a phone line?
o
How about
International Homologation?
o
Which
countries are the easiest? – Which are
difficult?
o
What is CTR-21? Does it
affect my design?
§
How does the modem effect Pt. 15A/B in my final
product?
o
Is there a way to keep the
EMI/RFI emissions to a minimum?
