Tyer’s electric tablet block system on the Upcountry railway: single-line token exchange mechanics?

Single-line train operations across the mountain railway adhere strictly to the historic Tyer’s Electric Tablet System (No. 6 instrument). The railway line is divided into discrete block sections. To enter a block (such as Nanu Oya to Ambewela), station masters communicate via electromagnetic telegraph bells. The instrument releases a single cylindrical brass tablet token; no second tablet can be extracted until the first is inserted into the receiving station’s machine. The tablet is locked into a leather pouch fitted with a large wire hoop. As the train passes the platform, the driver loops an arm through the station master’s hoop to snatch the token at speed.