Abraham,
The ISO1212 triggers based on the thresholds determined by the resistors. If the input signal is pulled down below the VIL threshold, then it will output low.
Hi Rajat:
Unfortunately, we don't have any alternatives for ISO1211.
If you're looking for a couple of samples, you may use our ISO1211EVM. ISO1211EVM is available from the eStore and Digikey.
Regards,
Dushmantha