function s = transmission(a,b,l,z,adm1,adm2)
% s = transmission(a,b,l,z,adm1,adm2)
% Model of a non-radiating transmission line between points a and b. 
% a, b :  Vectors [ax ay az] and [bx by bz] of transmission  end coordinates
% l    :  Length of the transmission line in m
% z    :  Impedance if the transmission line in Ohm
%         A negative sign in front of the characteristic impedance will act 
%         as a flag for generating the transmission line with a 180 degree 
%         phase reversal (crossed line) if this is desired.
% adma :  Complex admittance of a shunt at point a in S (default: 0)
% admb :  Complex admittance of a shunt at point b in S (default: 0)
% s    :  data structure of the transmission line 
