Hi everybody, I hope you can help. I am in Ireland and our national rail operator uses a number of paired frequencies in the 451 and 456MHz range but they all have a very annoying continuous tone when the channels are not in use. Once a radio is keyed I can hear one side of a conversation and then back to this high pitch tone. I can't find any information online about the system they use, only that they are moving to GSM-R. Is there a way to ignore the tone and only activate the scanner when there is speech. I have a Uniden SDS100. I have had to 'avoid' these channels because the scanner stops on the tone every time. Any help would be appreciated. thank you.