isolated 2-Wire bi-directional interface

I need your help with a schematic

I have got the challange to interface a PIC to a PC.

The PC will be located about 1500m away from the PIC.

There are only two wires available for the connection.
(No Common Ground)

The Interface must be optically isolated at both ends.

The Link must be bi-directional (Half Duplex)

Communication Speed should not be less than 4800 Baud.



Any Ideas ?

It looks like I have found a solution.

The MAX1480 is a completely isolated RS485 Transceiver that runs off a single 5V supply.

see Datasheet