  We have fabricated and studied a new kind of DC SQUID in which the magnitude
and sign of the critical current of the individual Josephson junctions can be
controlled by additional voltage probes connected to the junctions. We show
that the amplitude of the voltage oscillations of the SQUID as a function of
the applied magnetic field can be tuned and that the phase of the oscillations
can be switched between 0 and $\pi$ in the temperature range of 0.1 - 4.2 K
using a suitable control voltage. This is equivalent to the external
application of (n+1/2) flux quantum.
