In a manual block signaling system, train movements are governed through communication and authorization between block operators. The main safety principle is that only one train may occupy a block at any given time.
Before a train is allowed to enter a block, the block operator at the entrance of the block must confirm with the operator at the far end that the block is completely clear of other trains.
Communication between block operators may take place using telephones, telegraphs, block bells, or specialized signaling instruments that indicate the occupancy status of the block.
Once the receiving block operator confirms the block is clear, permission can be granted for the approaching train to enter the block. This authority is commonly given by displaying a clear signal indication or issuing a train order.
After the train enters the block, the block operator records the movement in the block register or train sheet and informs the next operator that the train has entered the section.
The block remains occupied until the entire train clears the far end of the block. Once the train has completely exited the section, the receiving operator communicates back that the block is clear again.
Only after this confirmation may another train be authorized to enter the same block. This step-by-step communication and authorization process ensures safe train separation and helps prevent collisions.
Accurate communication, proper record keeping, and strict compliance with operating rules are essential for safe operation under manual block signaling.