Alternatively, use the optocouplers for added safety. Something like the attached circuit will probably work (one copy for each signal). The output would not be quite a high or low as the voltage in is a sinusoid so you would get a square wave out so the added R-C circuit would correct this.
The other option is to connect the wires directly (well almost) to the microcontroller. "WAIT!" I hear you cry... won't that destroy it? Well, yes, that is where the almost comes in. Stick a 1M resistor in series and you wont.