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.

 

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ATO CMM 900-3W manual What is the flow control method recommended?