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8. FREQUENTLY ASKED QUESTIONS (FAQ)
Q1:
What is the flow control method recommended?
A1:
If the host is a PC, Hardware flow control is recommended.
However, in most control instrumentation, either software or no flow control is
called for.
Q2:
How do I disable any flow control?
A2:
Simply disable both the Hardware and software control switch settings. This is
not recommended for large file transfers.
Q3:
I need to connect the Cellular Data Link to a machine, which does not
understand your messages. All it needs is data. Which configuration is
recommended?
A3:
Please use the ATQ1&w&w1<CR> command.
Q4:
Have you experienced unreliable communication with certain modems?
A4:
Yes. Several generic brands tend to throw hot signals (i.e. strong signal levels)
on the line. This causes the cellular service to over-modulate, which leads to
distortions and results in unreliable connections.
Q5:
What is the solution?
A5:
We recommend that you use modems that support MNP-10 and also allow
transmit level to be reduced to between –15 dbm
à
–20 dbm. Rockwell based
modem designs generally meet these requirements.
For Rockwell based modems, please try the following commands
on the land line modem:
•
AT-SEC=1,18 <CR>. This will enable MNP 10 and set transmits level to
–18 dbm.
•
AT+MS=11,1,1200,2400X3&W&W1<CR>. Sets the modem to
communicate between 1200 and 2400 bps.
Q6:
Is there any simple way to avoid frequent loss of connection?
A6:
Please program the CMM 900-3W as follows
AT+MS=11,1,1200,1200&W&W1<CR>
This will force the CMM 900-3W to connect only at 1200 bps.
Q7:
What initialization string is recommended to communicate with non-MNP
modems?
A7:
Connection with non-MNP landline modems is not recommended.
