great, thanks for the reply.

stu

> The rectangles are available as the port outputs RB1...RB4 (pins 22...25) of
> the microcontroller. If you want to use these at outputs you have to insert
> protection resistors (~1k) between the corresponding pin and the sockets.
> Otherwise the microcontroller may be damaged when a plug is inserted into
> the socket (because of the short circuit that is generated for a short time
> when the plug is inserted).
>
> Best wishes
> Dieter Doepfer
>