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How to create a multiball with a traditional ball lock

Related Config File Sections:

Most pinball machines use a "virtual" ball lock to track multiball progress and MPF is designed to handle these by default. Machines that physically lock multiple balls require a few extra configuration settings to properly count locked balls and release them for a multiball.

Background](How MPF tracks and replaces balls

When a ball enters a ball device that is not the trough, the ball device checks for any locks that want to "claim" the ball. If the ball is claimed by anything, such as an enabled multiball_lock, the ball device will hold the ball and request a new ball be added from the trough to the playfield. If nothing claims the ball, the ball device will eject it back onto the playfield.

During this process, the number of "balls in play" never changes. When a ball is claimed by a lock, MPF simply swaps the location of the inactive ball from the trough to the ball device. From the game's perspective the playfield always has one ball in play.

Setting up a simple multiball

An MPF multiball only has one configuration requirement)


Be careful with with balls_to_replace and replace_balls_in_play. They will only work in exactly this combination. Used in isolation they will likely lead to incorrect ball counts.

Video about ball locks and multiballs:

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