Define LDAP query with objectclass

Hi

We have a 3. party software that can get information through LDAP but can't figure out how to define the search string.

If I type "OU=Test,DC=internal,DC=contoso,DC=local" it will return all users in the OU, but I need it to return contacts.

Is it possible to create a LDAP query where it looks in the above OU and only shows contacts?

Hopefully my question makes sense :-)

Lasse

/Lasse