For some time we have been planning to release a new version of Train Dispatcher 3 called Train Dispatcher 3 Pro. This new version was originally planned to be a paid upgrade to the existing Train Dispatcher 3. It was to have two new modes of operation called CTC Control and External I/O. The CTC Control Mode allows a user to control and monitor a model railroad by sending signal and switch commands to external hardware and receiving block, signal and switch status. The External I/O Mode allows Train Dispatcher 3 to be driven by an external CTC machine. Instead of using the mouse to clear signals and throw switches, Train Dispatcher 3, in this mode, will get these commands from an external machine. It will also provide signal, switch, and track circuit conditions back to the external machine as if the wayside equipment generated these conditions. We have been somewhat reluctant to release this new version, because of our fear that the amount of support some customers may require could not be justified by the price of the upgrade. However, we continually get inquiries on the release of Train Dispatcher 3 Pro. To resolve this dilemma I have decided to release Train Dispatcher 3 Pro (now called Train Dispatcher 3.5) as a free upgrade to Train Dispatcher 3 customers with the understanding that we will not provide free support to customers interfacing it to external hardware. Customers requiring support for the CTC Control and External I/O modes of operation will be able to purchase a support contract from us. Please note that Train Dispatcher 3 customers are licensed to use the CTC Control mode for non-commercial applications only. You are not licensed and are strictly prohibited from using this product to control a commercial railroad. Train Dispatcher 3.5 does not communicate directly with external hardware. Since there are many types of hardware interfaces, Train Dispatcher 3.5 relies on programs commonly called handlers that are specifically written to communicate with a particular piece of external hardware. These allow Train Dispatcher 3.5 to have one common interface for many types of external equipment. It also allows users to develop their own handlers for new types of equipment.