My train stopped in the tunnel today. "I lost the indication. Do you have it?" -- called out the operator to the conductor over the PA system. Sometimes instead of using walkie-talkies they use overhead PA to communicate. Probably by mistake, because hearing subway jargon spewing from the loudspeaker in a stopped train freaks out passengers.

"I lost the indication here too " -- said the conductor. We were stuck for at least half an hour before the train started moving again.

As it turns out, a signal is called and "aspect". For instance red light is a red aspect. And an "indication" is the meaning of an aspect in a context. Red aspect's indication is usually (but not always) - stop. So apparently what the machinist and the conductor meant was that the signal light they were expecting was off. When there is a power loss to a signal a trip arm automatically extends up from the track (it's up motion is powered by a spring, so it automatically engages when a signal loses power). If a train passes an extended trip arm it trips an on/off switch on the train and you get stuck for much longer.

I need to get a scanner with subway frequency.