  The effect of thermal fluctuations on the behaviuor of a 4-terminal SQUID is
investigated. The studied system consists of the Josephson 4-terminal junction
with two terminals short-circuited by a superconducting ring and other two form
the transport circuit. The behaviour of a 4-terminal SQUID is controlled by
external parameters, the applied magnetic flux and the transport current. They
determine the voltage in the transport channel and the magnetic flux embraced
in the ring. Within the numerical model the noise-rounded current-voltage
characteristics and the time dependence of the magnetic flux have been
calculated. In some region of the control parameters the 4-terminal SQUID is in
the bistable state with two magnetic flux values. The switching of the flux in
bistable state produced by the thermal noise or by the transport current is
studied.
