Mobile coverage along the Circle Line (CCL) will be suspended throughout Friday as the SMRT operator will do tests to identify the cause of signal interference.
"Due to ongoing tests, commuters travelling along the Circle Line will experience temporary suspension of telco signals," SMRT posted on its Twitter account.
Initially, the suspension was scheduled to end at 9 am. But, later Singtel and Starhub declared on their Facebook pages that the service disruption would last until the end of Friday. Howver, M1 said "until further notice" the suspension is in place.
According to SMRT, train services might be delayed due to intermittent signal interference. "For safety, CCL trains are manned this morning. We are sorry," SMRT tweeted.
On Wednesday morning, multiple delays and disruptions were caused by signaling issues on the Circle Line. It was quite similar to the trouble caused in September but the exact cause of the repeated signal interference is not yet determined.
Earlier, both Land and Transport Authority (LTA) and SMRT said they had launched feasibility studies to strengthen the communication of the existing signalling network.
They explored different options by placing an electromagnetic shield on the train to minimise the impact of interfering signals, and also tried changing the signal system frequency.