function [SN, DISP, RF, SPAR]=open_network_analyzer()
       SN=gpib('ni',0,14);       % 8501 storage normalizer, seems to be a natural talker 
        %  sinfo=propinfo(SN);      
       SN.inputbuffersize=4096;  % each character is a byte, need a large buffer! 
       SN.outputbuffersize=2048; 
       fopen(SN);
       clrdevice(SN);
       
       DISP=gpib('ni',0,16);
       fopen(DISP);
       set(DISP,'EOSMode','read&write'); % need do this to get it to "talk"
       set(DISP,'EOSCharCode','LF')

       RF=gpib('ni',0,3);
       fopen(RF);
       set(RF,'EOSMode','read&write');  % need do this to get it to "talk"
       set(RF,'EOSCharCode','LF')

       SPAR=gpib('ni',0,20);
       fopen(SPAR);