Solution:

The difference list about PCL-743/745 series is shown as follows: 1. Isolation: PCL-743 series => Non-isolation PCL-745 series => Isolation 2. TVS ( Surge Protection ): PCL-743B/745B => space reserved for TVS, not on board PCL-743S/745S => on board TVS ( 12 CA ) 3. Control mode: PCL-743/745 => Always on, RTS, register control PCL-743B/745B with A1 version => Auto PCL-743B/745B with A2 version => Auto, RTS, Always on PCL-743S/745S => Auto, RTS, Always on 4. Termination Resistor: PCL-743/745 => without sapce reserved for TR PCL-743B/745B => space reserved for TR PCL-743S/745S => space reserved for TR