PIU

PIU Subscriber unit 4 ISDN tributaries with U interfacem

Provides connection to ISDN exchange for 4 remote subscribers, via multiplexers FM2x2 and FM-MSAN
Single pair subscriber loop with 2B1Q line code
PIU-LT (Line Termination) and PIU-NT (Network Termination) options
PIU unit, as tributary unit within multiplexers FM2x2 and FM-MSAN provides connection of remote customer to ISDN exchange. User NT1 equipment is NT (network termination), whereas U-interface at exchange side is LT. Therefore, PIU unit at customer side must be PIU-LT, and PIU unit at exchange side PIU-NT.
Remote subscriber can be connected with ISDN exchange via more than one PIU-LT/PIU-NT pair, but maximum number of regenerators is six (i.e. three LT/NT pairs). For test purposes ISDN exchange can send diagnostic commands through EOC channel to each PIU unit in chain. 3 bits are reserved for address. "0" is address of NT1 equipment, "1" to "6" are for PIU units in chain, and "7" is for all stations in chain (broadcast).

4 ISDN U interfaces on PIU unit
One U-ISDN occupies 2.5 64kbit/s channels in FM2x2 and FM-MSAN
Position of U-ISDN in multiplex is configurable by management software
Transport via single pair is accomplished by use of 2B1Q line code with near-end echo cancellation
PIU-LT is equipped with remote power feed source, which can provide power feeding of NT1 without local power supply
Copper-pair interruption detectionShort-circuited copper-pair detection
Remote loopback control from ISDN exchange through EOC
Performance monitoring

PIU regenerators chain