We built a computerized 3-color signal system in 1999 for the Westchester Central RR with 18 blocks and 27 signals. Track occupancy and switch alignment were detected via rail circuits and passed to the computer which set the nearby home and distant signals accordingly.
CTI Electronics components were used, specifically their TBrain software and associated hardware.
The system was reinstalled on the Monadnock Valley RR in the summer of 2008. The MVRR has a number of long blocks and a train entering one end of the block cannot be seen from the other end. Thus the signal system is very useful in preventing "cornfield meets".