The ACS8515 is a highly integrated, single-chip solution for `hit-less' protection switching of SEC clocks from Master and Slave SETS clockcards in a SONET or SDH Network Element. The ACS8515 has fast activity monitors on the inputs and will implement automatic system protection switching against master clock failure. A further input is provided for an optional standby SEC clock. The ACS8515 is fully compliant with the required specifications and standards. The ACS8515 can perform frequency translation from a SEC input clock distributed along a back plane to a different local line card clock, e.g. 8 kHz distributed on the back plane and 19.44 MHz generated on the line cards. An SPI(1) compatible serial port is incorporated, providing access to the configuration and status registers for device setup.