driver vigilance or driver alertness system used by IR
Several loco classes have speed limiters with buzzers that go off when the prescribed speed is exceeded. In some cases these may also result in the application of brakes. Some WAP-4 locos have the buzzer system and it is set for a speed of 130km/h although they are capable of going faster, while a few WAM-4 locos have it at 110km/h (although not all WAM-4 locos have the buzzer system as it requires a relatively more recent speedometer assembly to be retrofitted in them). Some WAG-5 locos and others also have such warning systems. The WCAM-3 loco, limited to 105km/h by its bogies, has the buzzer set to its top speed.
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newer loco classes (WAP-5, WAP-7, WAG-9) have provisions in their original designs for setting a speed limit, which, if exceed results not only in the warning buzzer/light going off but also apply the emergency brakes to slow down to below the prescribed speed. This system, however, is not thought to be actually deployed in any of the locos currently in use. The top speed limit can be set in software (160km/h for WAP-5, 140km/h for WAP-7, 100km/h for WAG-9). In the WAP-5, WAP-7, and the WAG-9, the driver's job is easier in terms of not having to worry about exceeding the speed limit because these locos have provision for cruise control (constant speed settings) -- see above. However, the driver does have to activate the vigilance system periodically, as explained below, even when the cruise control is on.
Vigilance systems in the form of 'dead-man pedals' are provided in some locos, such as the WAP-7. In the WAP-7 system, the vigilance pedal (PVEF) has to be depressed periodically; alternatively a button on a panel can also be depressed. If this is not done, and if the master controller is not being used for braking or acceleration, and if the A9 or SA9 (train / loco brakes) are not being used (any of which temporarily override the vigilance system), an alarm is sounded. This must be acknowledged by the pedal or switch; if acknowledgement is not provided with 60 seconds, power to the traction motors is cut. If there is no acknowledgement within 10 seconds after this, the main circuit breaker (DJ) is opened and the brakes are applied bringing the loco to a halt. Resetting this afterwards involves a number of manual steps at the main computer unit ('HBB') and re-building brake pressure. A similar system is provided in the WDP-4 and WDG-4, as well as in the WAP-5 and WAG-9.