The CS61581 is a primary rate line interface unit capable of operation in both short haul (intraoffice) and long haul applications. The CS61581 combines the complete analog transmit and receive circuitry for a single, full-duplex interface at T1 and E1 rates. The device is pin and function compatible with the Level One LXT310 and LXT318 (the latter in the host mode only). The device can also replace LXT359 and LXT360. Enhanced functionality is available through an extended register set allowing short haul operation, custom pulse shape generation, QRSS pattern generation, detection and error counting, and generation and detection of loop up and loop down codes. The CS61581 features Crystal low-power impedance-matched line drivers and crystalless jitter attenuation.