Hi Ewan
This device IS both ways. Block diagram of the driver…
BUT not both ways at the same time, ie; Half Duplex only.
Please read the above thread completely. You will probably find most of your questions answered.
If you look at the circuit I think R5 and R6 should be removed and R7 only used AT THE CABLE ENDS. That means if you only have 1 device at each end it would be OK to leave ir but if you are using several (read more than 1) intermediate devices this resistor should be removed on those.
What the other pull ups are for I don’t know. All of these resistors are discussed above.
In short if you have one of these at each end of a twisted pair (A & B lines) you should be able to insert TTL at one end and extract the same TTL at the other end BOTH WAYS.
Cheers Bob
