  We used the newly commissioned 50 cm Binocular Network (50BiN) telescope at
Qinghai Station of Purple Mountain Observatory (Chinese Academy of Sciences) to
observe the old open cluster NGC 188 in V and R as part of a search for
variable objects. Our time-series data span a total of 36 days. Radial velocity
and proper-motion selection resulted in a sample of 532 genuine cluster
members. Isochrone fitting was applied to the cleaned cluster sequence,
yielding a distance modulus of (m - M)0V = 11.35 \pm 0.10 mag and a total
foreground reddening of E(V - R) = 0.062 \pm 0.002 mag. Light-curve solutions
were obtained for eight W Ursae Majoris eclipsing-binary systems (W UMas) and
their orbital parameters were estimated. Using the latter parameters, we
estimate a distance to the W UMas which is independent of the host cluster's
physical properties. Based on combined fits to six of the W UMas (EP Cep, EQ
Cep, ES Cep, V369 Cep, and--for the first time--V370 Cep and V782 Cep), we
obtain an average distance modulus of (m - M)0V = 11.31 \pm 0.08 mag, which is
comparable with that resulting from our isochrone fits. These six W UMas
exhibit an obvious period-luminosity relation. We derive more accurate physical
parameters for the W UMa systems and discuss their initial masses and ages. The
former show that these W UMa systems have likely undergone angular-momentum
evolution within a convective envelope (W-type evolution). The ages of the W
UMa systems agree well with the cluster's age.
