The following circuit board(s) are compatible with the above topside: 59-553-1000
On 10/7/2009 United changed the type of connectors for the topside and the transformer from a RJ45 to 8 pin Molex and in 2012 changed to a 10 pin Molex. ;If you are replacing just a board or topside insure you have the correct topside adapter cord for your configuration: