| 摘要 |
A switching apparatus for a player piano or other keyboard instrument including an elongated extrusion which supports a tracker bar means positioned between the roll carrier and the take-up roll of the player piano. The tracker bar means has a plurality of spaced apart air passageways formed therein which are adapted to sense the perforations in the sheet material passing thereover. Each of the ports have a conduit means communicating their width and extending therefrom. One embodiment of the invention includes a bellows type element on the nipple which expands to close a switch when the respective air passageway registers with a perforation in the sheet material. Another embodiment of the invention includes a movable capsule at the end of the nipple which moves to close a switch when the respective air passageway registers with a perforation in the sheet material. The switches are electrically connected to a solenoid and activates the same when the switch means is closed by the expansion of the element on the conduit means. The extrusion supports the tracker bar means, circuit board, terminal bar and electrical leads.
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