Data Transfer modes

Normal Response Mode (NRM)

A Secondary station running in an Unbalanced communications environment may may only communicate when signalled to do so by a Primary.

Asynchronous Balanced Mode (ABM)

hen in a Balanced communications environment, either Combined station may initiate communications. (LAPB Mode on combined stations only.)

Asynchronous Response Mode (ARM)

When in an Unbalanced environment, the Secondary may transmit at will, however the Primary is still responsible for error detection, line and flow control.