Historic Transistor Photo Gallery

Photo Essay – Bell Labs Bead Type Point Contact





Assembly View of Cartridge and Bead Type Transistors




Unique Hybrid Sample Point Contact Transistor


Photo Essay Commentary

The two transistor types illustrated in the drawing above (left) represent the mature versions of the cartridge type and the bead type point contact transistors at Bell Labs/Western Electric through the mid 1950s [4].   The cartridge type had evolved from the earlier Type A transistor [1] and the bead type had evolved from the small circular plastic bead experimental type shown earlier in this photo essay.  The photo (above right) represents an experimental, hybrid case point contact transistor – it is likely that this approach was used to take advantage of the socket mount capabilities of the cartridge type.


The model numbers used to identify developmental and the corresponding RTMA/Jetec numbers for all documented bead type BTL/Western Electric point contact transistors are shown in the table below [5].


Bell Labs

Western Electric

Type Number



RTMA/Jetec Number






Go To PhotoGallery Bead Type Pct Page 5




Copyright © 2004 by Jack Ward. All Rights Reserved.