deviceType in connection string

[sqlProg]

I am trying to do screen scraping of one of my mainframe screen. Below is the connection string that I am specifying in my code
string _connstring = "Transport=TN3270;TN3270Server=tn3270.mvsprod;TN3270Port=23;DeviceType=IBM-3278;";

// create a sessionDisplay and connect

SessionDisplay _sessionDisplay = new SessionDisplay();
_sessionDisplay.Connect(_connstring);

when I come to this line _sessionDisplay.Connect(_connstring);, I get this error "The value 'VT100' for tag 'DeviceType' in the Connection String is not one of tha allowed strings."

I am getting this device type from mainframe itself options-> settings and then connection and in the connection the device type is specified as IBM-3278. I don't know wwhere to get the device type from. Can anyone help me with this device type.

Thanks.