The fault affects all services heading between Glasgow and Edinburgh via Falkirk High, along with services through Falkirk Grahamston and Polmont.
The problem is located at Haymarket and is expected to continue to cause issues until this afternoon.
ScotRail says replacement buses have been requested at a number of stations, including Falkirk High, Falkirk Grahamston and Polmont.
There have already been cancellations to some services this morning, with all trains on the route subject to delay or revision.
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ScotRail say Network Rail are already working on the problem and hope to have it fixed this afternoon.
A ScotRail spokesperson said: “We are sorry to customers for the disruption to their journey, which has been caused by a signalling fault.
“Network Rail engineers are working hard to fix the fault and we are doing everything we can to keep people moving.
“Replacement buses have been put in place at stations throughout the affected routes and we have also secured ticket acceptance wherever possible, including Edinburgh trams and Lothian buses.
“Customers are asked to check @ScotRail on Twitter or the ScotRail app for the most up to date information.”
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