The ZL30410 is a Multi-service Line Card Phase-Locked Loop designed to generate multiple clocks for SONET, SDH and PDH equipment including timing for ST-BUS and GCI interfaces. The ZL30410 operates in NORMAL (LOCKED), HOLDOVER and FREE-RUN modes to ensure that in the presence of jitter and interruptions to the reference signals, the generated clocks meet international standards. The filtering characteristics of the PLL are hardware pin selectable and they do not require any external adjustable components. The ZL30410 uses an external 20 MHz Master Clock Oscillator to provide a stable timing source for the HOLDOVER operation.