hi vivek,

problem is that

1. if you or the signals noway you can diferertiate between them, tf this is the need, three diode (1N4148) will do the job. if your output where you are getting input from, are open drain/collector even dioded are not required.

2. if you want to diferentiate between them you will need 1-4 line multiplexer which requires lines for selection and one line for input itself. that means that totals to three i/o pins. connect them directly without any MUX.

abhishek