function xdot=ad_sys(t,x)
%AD-ODE is a script that implements A/D conversion using Tank-Hopfield net

% Written by S. H. Zak on May 29, 1999

global a;
xdot=[-(2*x(2)-a+1/2)*4*x(1)*(1-x(1));-2*(x(1)-a+1)*4*x(2)*(1-x(2))];