Abstract: A closed loop transmission system is described in which a plurality of stations have access to each loop to write messages into and read messages from standard-sized message blocks transmitted around the loop. One station in each loop provides regeneration of all message blocks. The various loops are interconnected by switching stations which respond to address information at the head of each message block to selectively switch the block to the interconnected loop. The next required address is always substituted for the current address to simplify address recognition. Alternate and redundant routing are also provided for.

Abstract: An echo suppressor for full duplex telephone circuits consists of a filter bank of contiguous band filters in the transmission path, with each filter output feeding a separate center clipper. Each clipping level is controlled by echo signal amplitude as attenuated by the trans-hybrid loss that occurs in the corresponding subband. The scheme permits "double-talking" while suppressing the echo component.