no "OK" answer on hangup with pulse DTR (AT&D2)

Hi,

The modem Fastrack Supreme is used on GSM DATA V32 9600bds.

My problem is : when the hangup is done by a pulse of DTR = -9V / 1,2s, the modem dosen’t answer “OK” !
With the Fastrack M1306B, no problem.

do you have an idea ?

Gaby