Use to specify the hexadecimal base device number associated with the CTC adapter; 6B2, for example. This is also known as the unit address.
Rules:
The device number must be greater than or equal to 0, and less than or equal to FFFF.
Two numbers are used by TCP/IP: the base device number and the base device number+1. One of the device numbers is used as the READ channel and the other is used as the WRITE channel.
Indicate whether the device number entered is the READ or the WRITE channel.