Norwegian railway signaling
[2] On these lines, the dispatcher and drivers had to communicate using the Nordic Mobile Telephone (NMT 450) standard, a system which the operator Telenor discontinued in 2002.If the yellow lamp fails, a relay will also switch off the green light and the signal becomes totally dark, which is then treated as "expect stop."Hence, if the yellow lamp does suddenly fail, the green light will blink alone 1-2 times before it is switched off by the relay.Note: The animated picture of signal 24 is wrongly giving the impression that the yellow light is shown before the green one.Norway uses the Ericsson ATP warning system, also used on Perth's suburban railway network.