Question : Configuring a 2811 router to acts as Call Manager for VoIP with 7940

Cisco 2811
IP Phones 7940
NM-16ESW-PWR
VIC2-2FXO
WIC-ATM-DSL

What I Want to do is to have a config where I can do calls from/to internal extensions using IP Phones and also with them, I can receive from external calls over the single phone line. My understand is when some external call comes is going to the phone number (vic2-2fxo will forward the call), then the traffic should be addressed to only one extension (a central), and then if I need to transfer it, I can do it from IP Phone to IP Phone (over the extensions) or even pick it up from any IP Phone. Is this possible with the hardware listed before? And if you have some examples in order to guide me

Also this router is a DSL gateway/firewall and acts as VLANs router too, but this is not my problem, my challenge is to config the voice traffic, and to create the IP Phone environment with access to external world :D

Many thanks in advance

Answer : Configuring a 2811 router to acts as Call Manager for VoIP with 7940

here is the configuration:
telephony-service
ip source x.x.x.x(any active interface loopback is recommended)
max-ephone x(maximum number of phones)
max-dn x(maximum number of extensions it could be bigger than ephones)
create cnf
!! this configuration is for simple CME

ephone-dn 1 dual-line
number 1000 (extension number)

ephone 1
mac xxxx.xxxx.xxxx(mac address of the phone)
button 1:1(associate first button with ephone-dn 1)
button 2:1(associate button 2 with ephone-dn 1)
type 7940

just configure all the phones like this example or you can make it automatically.

for FXO ports
if you want the call to go directly to one extension
voice-port x/x/x
connection plar opx 1000

to make a call

dial-peer voice 1 pots
destination-pattern 911
forward-digit all
port x/x/x

if you want more information i will be with.