1.  SMRT and LTA have established the presence of an interfering signal in the Circle Line (CCL) tunnel within the operating frequency band of the signalling system. This interfering signal could be a possible cause of the intermittent loss of train-to-track communications. However, experts have not yet been able to verify the source.


Update from 2 September investigations

2.  Telecommunication signals in four CCL stations (Kent Ridge, Haw Par Villa, Pasir Panjang and Labrador Park) were suspended yesterday evening between 7 pm and 9 pm to assist in the investigation. More tests were also conducted throughout the night between 1 am and 4 am. However, as there was no incident last evening, the tests were inconclusive. In fact, since 4 pm yesterday, there has not been any intermittent loss of signal communication of train-to-track communications.

3.  SMRT and LTA are continuing with the investigations. Should and when an incident recur, SMRT and LTA have worked with the Infocomm Development Authority (IDA) and mobile network operators to suspend telecommunication signals along stretches of CCL for short periods of time for further tests. If temporary telecommunication signal suspensions have to be carried out, there will be in-train and station announcements along the affected stretches.

4.  We seek commuters’ understanding and patience as we press on with our investigations.