I went to this site http://www.beta-a2.com/ and this is the quote they gave me for networking four rs-232 machines together.
For 4 CNC machines as described above the components and wiring might run in the range of:
5 I232 $500
1 Switch $350
5 Cables 75 + 120*4*0.55 $339
Shipping and handling $ 80
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$ 1269 as an estimate
Does that sound about right?
thanks,
Tim Pehlke