This photograph shows a BTH magnetic track brake as installed in the Brill 22E truck used for all Bournemouth's bogie cars.

The brake shoe comprises three elements, with a magnetic circuit being formed between the centre shoe and the extension shoes on each side, through the rail.

This arrangement was superior to pure mechanical track brake as it did not unload the wheels, which would cause the tram to be more likely to slide when using the service brake.

Track brakes and their operation came under close scrutiny in Bournemouth after tram 72 ran away on Poole Hill on 1-May-1908, an accident resulting in seven fatalities. This may be a reason why this photograph was taken.

The two white circles at the top are where the photograph was punched for filing.

Photograph from the GEC archive