I am the secretary at my church and we have an older Comdial Executech phone system which was installed several years ago by a volunteer. Unfortunately, we can't seem to figure out how to use the various features. One in particular is the intercom at our door which is supposed to be hooked up to our phone. When someone rings the doorbell it just beeps on the phone, but we can't figure out how to talk to them thru the intercom. Also, we tried once to hook up an answering machine but it wouldn't work. Any help would be appreciated!