ahmedsa
I doubt in telephone line connected to Cisco firewall router.
My question How i know that telephone line connected with Cisco router is working or offline
You would typically connect a Windows workstation or similar computer (ie the NIC port) directly to your router (with the physical connection to sme server & the rest of the network disconnected), & login as admin to the router via a web browser, again typically to 192.168.1.1 (but that will depend on your router & what settings have been made to it).
Then you will see control panel(s) & typically there are pages that will show the external connection, speed, activity, connection protocol etc & perform diagnostics for you.
This should all be detailed in the router Manual, so please read it, as has been advised already.