If you are using and older model or a cheaper GSM modem, it might be
possible that the modem cannot handle data coming at high speed from
the computer. This issue is handled in Ozeki NG SMS Gateway. You can enable
slow modem communication in the GSM Modem configuration form.
To enable Slow modem communication please open the GSM modem configuration
form, select the "General settings" tab and in the "Timeout handling"
section check the "Slow down modem communication" checkbox (Figure 1).