  A modification of the symmetry approach for the classification of integrable
differential-difference equations of the form $$ u_{n,t} = f_n(u_{n-1}, u_n,
u_{n+1}), $$ where $n$ is a discrete integer variable, is presented (the
well-known Volterra and Toda equations can be written in this form). If before,
in the framework of the symmetry approach, only equations similar to $$ u_{n,t}
= f(u_{n-1}, u_n, u_{n+1}), $$ i.e. defined by a function $f$, were considered,
now we have an infinite set $f_n$ of a priori quite different functions.
