We consider a family of M(t)/M(t)/1/1 loss systems with arrival and se
rvice intensities (lambda(i)(c), mu(t), (c))=(lambda(ct), mu(ct)), whe
re (lambda(t), mu(t)) are governed by an irreducible Markov process wi
th infinitesimal generator Q=(q(ij))(mxm) such that (lambda(t), mu(t))
=(lambda(i), mu(i)) when the Markov process is in state i. Based on ma
trix analysis we show that the blocking probability is decreasing in c
in the interval [0, c], where c*=1/max, Sigma(j not equal i) q(tj)/(
lambda(i)+mu(i)). Two special cases are studied for which the result c
an be extended to all c. These results support Ross's conjecture that
a more regular arrival (and service) process leads to a smaller blocki
ng probability.