Hi Biplob,
The difference between balanced and unbalanced network module is the resistance (ohm). Balanced has a resistance on 120 ohm and unbalanced has 75 ohm of resistance.
The decision to go with either a balanced (120 ohm RJ-45) or unbalanced (75 ohm BNC) interface for an E1 ISDN PRI is generally based on what the ISDN service provider offers for the service.
The major difference between E1/ISDN PRI Balanced vs Unbalanced cards involves the hardware design of the telco interface to which the port adapter connects to. The balanced interface uses both tx and rx tip and ring actively in it's circuitry and the unbalanced inerface uses tx and rx tip
signal to interact with shield (ground). The difference in physical characteristics of the unbalanced interface will allow for a much greater distance of cable run.
Hope it clarifies you.
Thanks,
satish
