Automatic Block system, automatic authorities, how to pass automatic signal at ON 

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Automatic Block system, automatic authorities, 9/A912,9/B912,9/C912,9/D912. how to pass automatic signal at ON.
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#automaticblocksystem
#authorities
#automaticauthorities
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#T/A912
#T/B912
#T/C912
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#passautomaticsignalaton
#signalaton
#howtopassautomaticsignalaton