Tennis play duration controller - has clock switching off electromagnet holding rope drum of raised tennis net

摘要

The automatic timing of tennis play is ensured by a watch controlling electromagnets of the tennis net. The magnets hold the net in the play position, and at the end of game period de-energisation fo electromagnets take place with a dropped net preventing further play. The electromagnet (g) is mounted on a shaft and features coupling claws for engaging the rope drum (e) against a return spring (e"). De-energisation of the electromagnet releases the drum allowing drop of the tennis net by gravity.