Topology: U1930 ---- AT0 ---- PSTN
When somebody make an incomming call to the automatic switchboard, the caller will not be forwarded to the extension after pressing the extension number. after pressing the extension number, the caller number still got the VU announcement , it seems that U1930 didn't know the caller has dialed any key.
From the phenomenon we think U1930 didn't regonize the DTMF signal, there are 2 possible resason:
1. there is something wrong on the operator devices , when the mobile pressing keys, operator didn't send DTMF signal to U1930.
2. Operator send DTMF signal to U1930, but the parameters is not standard (voltage, frequence) , cause U1930 receive it but cannot regonize it.