The TP3401 TP3402 and TP3403 are complete monolithic transceivers for data transmission on twisted pair subscriber loops They are built on National's double poly microCMOS process and require only a single a 5 Volt supply Alternate Mark Inversion (AMI) line coding in which binary `1's are alternately transmitted as a positive pulse then a negative pulse is used to ensure low error rates in the presence of noise with lower emi radiation than other codes such as Biphase (Manchester) Full-duplex transmission at 144 kb s is achieved on a single twisted wire pair using a burst-mode technique (Time Compression Multiplexed) Thus the device operates as an ISDN `U' Interface for short loop applications typically in a PBX environment providing transmission for 2 B channels and 1 D channel On 24 cable the range is at least 1 8 km (6k ft)