Another thing I forgot to mention about the dial intercoms. They usually have some audible feedback to the user in the form of a dial tone of sorts and usually a tone indicating signalling. No such joy with the manual intercom cards. You pick up the phone with a manual card and you just hear dead air until someone picks up. The majority of the dial intercoms are a one shot affair as far as signalling. You dial a number and it gives one burst of signal then that's it. They don't usually keep ringing like a normal phone line. Most have the ability to re-signal if it's a touch tone model. I think it's either the star or pound key that will re-signal the called station, often times for as long as you hold the key down. I know my valcom is like that. My personal opinion is I wouldn't waste a card slot in a KSU that only has four slots on a manual card. Might be kind of neat for a private circuit like boss and receptionist or two partners in a law firm kind of deal, but for a general intercom, DICM all the way!