Oh, and I did a tcpdump to see what data is coming in. Here is the result:
10:53:07.731193 IP 192.168.0.121.sip > 192.168.0.22.sip: SIP, length: 501
10:53:07.734563 IP 192.168.0.22.sip > 192.168.0.121.sip: SIP, length: 513
10:53:07.833639 IP 192.168.0.121.sip > 192.168.0.22.sip: SIP, length: 754
10:53:07.836984 IP 192.168.0.22.sip > 192.168.0.121.sip: SIP, length: 513
10:53:07.940895 IP 192.168.0.121.sip > 192.168.0.22.sip: SIP, length: 754
10:53:07.944430 IP 192.168.0.22.sip > 192.168.0.121.sip: SIP, length: 513
10:53:08.048397 IP 192.168.0.121.sip > 192.168.0.22.sip: SIP, length: 754
10:53:08.052214 IP 192.168.0.22.sip > 192.168.0.121.sip: SIP, length: 513
192.168.0.22 is the server and 192.168.0.121 is the 7940.
Looking at the Asterisk CLI, there is no activity relating to the phone being shown.