Western Electric 557D  
Written by Accutron on 2017-02-10  

The 557D is an unusual hybrid controller IC from a Western Electric Trimline telephone handset. The 557D is constructed from a multiple layers of ceramic, with discrete semiconductors and passives bonded together within the substrate. The 557D has numerous serpentine tracks of resistive material etched onto the ceramic. Earlier versions of this device were built upon a glass substrate.

Western Electric 557D hybrid integrated circuit.

This article is part of the [Digital Integrated Circuits] exhibit.

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