Cisco IP phone 7912G-A is a Cisco Unified IP Phone 7912 with hardware update.7912G-A has an additional ethernet port for QM support whereas 7912G does not have.QM is supported only in the following phones and not on 7912G.
7940,7960,7970,7911G,7912G-A,7941G,7941G-GE,7961G,7961G-GE,7971G and IPCommunicator Soft Phone.