A diagnostic test that sends a pre-defined set of bits to a node. These bits are bounced off the node and return to the host. The signal strength is meausured upon its return. This can be done locally or remotely. The loop up code and test pattern are sent together using overhead. Alternating loops are used on circuits that are 56k DS0 and below. This loop can not be performed on a 64k circuit because there are no bits of overhead on the channel.
Alternating loopback
