Help with Schematic-Trying to make a MODEM

[FromTheCockpit]

Could you please also tell me what VOL, VOH, VIH, VIL actually means and which ones are the one to look for next time I want to connect any device to my PIC. Thanks

[Jerson]

VOH and VOL are the voltages you get when the device sets its output to High or Low. VIH and VIL are the voltages the device expects to interpret the value as a 1 or a 0.

For VDD_ext = 3V, you should ideally be using a PIC that can operate at 3V.

[FromTheCockpit]

Thanks for replying. My PIC will be running on 4V actually. Will it be able to accept data with those outputs of between Gnd & 2.73V ?

If yes then I assume I can connect the module pins directly to the PIC without any amplifier circuit in between. Is that correct?