The point motor is powered by 110V d.c. supplied by the nearby relay house. When an order is given to switch the point, power is given to the motor in the respective direction. The motion is used to either push or pull the drive rod. Point machine has contacts for detection of the switching. These contacts are operated by the long and short detection rods. When the point is set properly an indication is obtained by the relay house through these contacts. The allowable gap between the stock rail and the switch blade is 3mm. When a foreign material such as a stone prevents the point from setting properly, the indication contacts stay neutral and no indication is sent. The clutch mechanism in the point machine will start slipping in order to protect the machine from mechanical damages. The safety relay attached to the motor circuit will cut off power in 15 seconds. When no indication is obtained at the control office, the controller will inform the Signal and Telecommunication Inspector (STI) in charge of the respective yard. On receipt of the information, STI will go to the motor point in question and remove the obstacle. The point machine has a facility to operate it by manual cranking. Once the point is cranked, the operation is finished and the indication will received by the control office.

Some points in the color light area are of lever frame type. They are not frequently switched during routine operations. These type of points are protected by a device called "magnetic lock", which has to be released by the controller at the central office to enable station master to switch the point. After the  operation is completed station master will switch the point back to its normal position and it is locked by the controller. This ensures that all the points are under the controller at the central office.

© R. Jayanthan
Last updated on 01 January, 2002