We are currently shipping Firmware 3.09 in our GSM Dialer boards. There are no apparent differences between 3.08 and 3.09 to the user and even installer. However the software is considerably different to the point where we cannot remotely flash the unit over the air (this can only be done for small updates).
For 3.09 we have introduced a software Low Pass Filter (LPF) in addition to the hardware LPF on the inputs. Whilst the software filter is of similar duration to the hardware filter, it is able to filter RF high energy surges which the hardware filter may pass (despite the opto-coupler). The minimum input duration of a pulse or step input is now 2mS.