The LH1539 telecom switch consists of an optically isolated solid state relay (SSR) Form A and a bidirectional input optocoupler in a single 8-pin package. The SSR is ideal for switchhook and dial-pulse switching while the optocoupler performs ring detect and loop current sensing functions. Both the SSR and optocoupler provide 5300 VRMS of input-to-output isolation voltage. The SSR is integrated on a monolithic receptor die using smart power technology. The SSR features low ONresistance, high breakdown voltage, and current-limit circuitry that protects the relay from telephone line induced lightning surges.