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Even post-WWII buyers could still purchase the descendants of the NC-100 in the modernized NC-240D receivers.
The front of the coil catacomb had a "track" machined into it and the band change shaft, which also carried a pinion gear, protruded beyond the pinion gear and rode in this "track," thus supporting the front of the catacomb.
The rack gear was mounted to the front of the catacomb at the proper level to engage the pinion gear to allow moving the catacomb via the band changing shaft.
The "detent" action was actually caused by the 15 coil pins engaging the 15 contacts which provided the positive feel of the catacomb "locking" into position.
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Includes NC-100, NC-101X, NC-80X, NC-81X, NC-100A family, NC-200, NC-240CS, NC-240D Dept of Commerce & CAA Airway Communication Receivers Military Versions - RAO family, RBH, NC-100ASD, R-115, R-116 History of Design and Production, Moving Coil Catacomb Details, WWII Versions, Post-WWII Production, Serial Numbers, Restoration Write-ups Besides National's masterpiece, the HRO, another series of receivers produced by National Company, Inc.