Loop Telecom's V.35/V.36/EI530/RS232/X.21 plug-in cards are a series of 4 different plug-in cards designed for the Loop-AM 3440-A series. They allow muliplexing of n x 64 Kbps data to multiples of DS0 time slots onto a digital network.
An LED on the front panel of the Loop-AM 3440-A provides status indication.