The 1800 series routers do not have voice capabilities to enable the use of CME, SRST, VWICs, etc., however you could certainly have a phone at a remote office that registers with the CallManager at another office. You cannot simply use an IP phone at each office. In this scenario, you have to be concerned with QoS (delay, jitter, loss) on the link.
What is your telephony environment? Do you have a CallManager? Do you plan to implement VoIP? In this case you just have to configure DHCP with a proper settings for the phones, and add them to your CallManager.
If you just want to use IP Telephone as an eventual communication method, then you could just use Microsoft NetMeeting - you can configure "peers" and start conversations using your local phonebooks.
If you want to go more advanced way, you can install some kind og VoIP Gatekeeper or IP PBX (for example, Asterisk), and install SIP/H.323 phones or ATAs.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.