We all know that there is HPDB 50 pin connector and D-sub 50 pin connector, because these two type connector is 50 pin connector, so it is easy to mix them. There are two ways to tell them apart.

1.Connector appearance: 

HPDB50 connector is also named HD50 pin connector or Micro DB 50 pin connector, this 50 pin connector pin arrangement is in two rows, one on top of the other. The top row has 25 pins and the lower row has 25 pins.

While D-sub 50 pin connector is also named DB 50 pin serial connector, this 50 pin connector pin arrangement is in three row. The top row has 17 pins(Pin1 to Pin 17), middle row has 17 pins (Pin18 to Pin33), lower row has 16 pins(Pin34 to Pin50)

2.Different Application 

HPDB50 connector is always used on SCSI device, such as SCSI hard Drive, Parallel printer with SCSI Connector, Motion controller with SCSI Connector and other SCSI scanner.

DB50 pin connector is always used on serial device or automatic devices.

We also can distinguish HPDB50 connector and DB50 pin connector from their connector size.

Here is commonly HPDB50 connector cable and DB50 pin cable, you can find the difference directly.

DB 50 Pin Male To 50 Pin Male Cable

HD 50 Pin Male SCSI Cable Assembly