Tobias I really thank you for dealing with my problem. Let me explain a little better the situation.
I use OPEN-AT 3.01 with 650a software in Q2406b.
I made some tests and realised that this problem (behaviour) appears in every sample application I have tried.
I will try to describe it again more clear I hope.
I have two modems A and B. In modem A I have a very small OPEN-AT application running (its a demo appl that handles sim events). In modem B I have no application running.
So what I do is: With Hyperterminal I make a data call (atdxxxxxx) from modem B to modem A. The call is answered (autoanswer - ats0=2)and I see Connected 9600 in both hyperterminal windows.
My problem is that While connected:
In modem B I write something i.e. “hello” but doesn’t appear in modem A
In modem A I am trying to send a string i.e. “hello” but I realise I am still in at mode (instead of circuit switched -CSD data mode) and everything I write is not transmitted to modem B. I tried to go to data mode with “ato” but nothing … still in at mode 
Why this is happening??? I haven’t made any fcm subscriptions. Is it standard behaviour and how can I avoid it?
While CSD connected I need to have a direct channel from uart1 of modemA to uart1 of modem B. Which is the standard behaviour when no OPEN-AT application is running on any modem.
Please. Can Wavecom OPEN-AT more Advanced Programmers help a newer member like me? It would be really helpful 
.
Should I try fcm subscriptions to GSM flow and Serial Flow and copy the data from the one flow to the other???
My simple demo application is the following, but the behaviour is the same with every sample I have tried (hello_world, telemetry):
#include “adl_global.h”
/***************************************************************************
Mandatory variables
wm_apmCustomStack
wm_apmCustomStackSize
****************************************************************************/
u32 wm_apmCustomStack [ 256 ];
const u16 wm_apmCustomStackSize = sizeof ( wm_apmCustomStack );
/***************************************************************************
Function : SimCard
Description: Display the SimCard Events
Variable Name |IN |OUT|GLB| Utilisation
----------------------±–±--±–±----------------------------------------
Event | | | | Sim Card Events
----------------------±–±--±–±----------------------------------------
****************************************************************************/
void SimCard (u8 Event){
switch(Event){
//Normal Events
case ADL_SIM_EVENT_PIN_OK:
adl_atSendResponse ( ADL_AT_UNS, “PIN Code Ok\n\rConnecting to network…”);
break;
case ADL_SIM_EVENT_REMOVED:
adl_atSendResponse ( ADL_AT_UNS, “SimCard Removed\n\r”);
break;
case ADL_SIM_EVENT_INSERTED:
adl_atSendResponse ( ADL_AT_UNS, “SimCard Inserted\n\r”);
break;
case ADL_SIM_EVENT_FULL_INIT:
adl_atSendResponse ( ADL_AT_UNS, “Ok SIM Full Init Succeded\n\r”);
break;
//Error Events
case ADL_SIM_EVENT_PIN_ERROR:
adl_atSendResponse ( ADL_AT_UNS, “PIN Code Incorreto\n\r”);
break;
case ADL_SIM_EVENT_PIN_WAIT:
adl_atSendResponse ( ADL_AT_UNS, “Please insert PIN Code\n\r”);
break;
}
}
/***************************************************************************
Function : adl_main
Description: Main function
Variable Name |IN |OUT|GLB| Utilisation
----------------------±–±--±–±----------------------------------------
InitType | | | | Application start mode reason
----------------------±–±--±–±----------------------------------------
****************************************************************************/
void adl_main ( adl_InitType_e InitType )
{
TRACE (( 1, “Embedded Application : Main” ));
adl_simSubscribe(SimCard,NULL); //Simcard events
}
