  Two graphene-based T-shaped multifunctional components for THz and
Far-Infrared regions are proposed and analyzed. The first component can serve
as a divider, a switch and a dynamically controllable filter. This T-junction
presents a circular graphene resonator and three graphene waveguides with
surface plasmon-polariton waves connected frontally to the resonator. The
resonator can be adjusted to work with dipole, quadrupole or hexapole modes.
The graphene elements are deposited on a $SiO_{2}$ (silica) and $Si$ (silicon)
two-layer substrate. The dynamical control and switching of the component is
provided by the electrostatic field which defines the graphene Fermi energy.
Numerical simulations show that the first component in the division regime
(which is also the regime ON) has the transmission coefficient -4.3 dB at the
central frequency for every of the two output ports and the FWHM is 9.5$\%$. In
the OFF regime, the isolation of the two output ports from the input one is
about -30 dB. The second component is a T-junction without resonator which
fulfils the function of the divider-switch in more than octave frequency band.
