We have Cisco SCCP IP Telephone 7945 and Wireless IP Telephone 8821 configured in CME.
Both are shared line and configured with the same extension.
The issue was when someone call from outside/external either mobile or other landline number the ringing is diverted only to IP Telephone 7945 not in Cisco Wireless 8821 Phone. the below sample configuration are as follows:
Wireless
voice register dn 1
number 1001
shared-line max-calls 16
SCCP phone
ephone-dn 1 dual-line
number 1001
shared-line sip
Thanks and Regards,