Pretty much. A signal tower usually controls several stations, so delays up ahead are usually contained within the zone of control of a signal tower. In cases

Pretty much. A signal tower usually controls several stations, so delays up ahead are usually contained within the zone of control of a signal tower. In cases where delays are more substantial and you need to hold trains further upstream, this is communicated manually between towers. Much of the control here is not based on semantic data, but rather verbal. The actual control system itself isn't capable of much more than indicating which piece of track is occupied.