10PACK Low-Power NPN Germanium Switching Transistor: A vintage, hermetically sealed point-contact or early junction germanium transistor housed in a distinct metal-can package, engineered under proprietary Bell Labs / Western Electric specifications to handle high-reliability low-voltage signal logic and amplification. Unit Sourcing Compatibility: Legacy telephone switching systems, central office routing racks, early AT&T Bell System microwave relay equipment, and mid-20th-century analog telecommunication modules manufactured by Western Electric / AT&T. Exact Industry Equals: AT&T 138A, Western Electric 138A, and Bell Labs 138A. Technical Specifications & RatingsBecause this is a classic milliwatt germanium alloy-junction device, its tolerances reflect the low-voltage, temperature-sensitive constraints typical of mid-20th-century semiconductor design:Polarity / Type: PNP Germanium Alloy-Junction.Maximum Collector-Base Voltage (\(V_{CBO}\)): -30 Volts DC (Maximum rating before junction breakdown).Maximum Collector-Emitter Voltage (\(V_{CEO}\)): -20 Volts DC (Sustaining threshold across the load path).Maximum Emitter-Base Voltage (\(V_{EBO}\)): -5 Volts DC (Highly sensitive input junction barrier).Maximum Continuous Collector Current (\(I_{C}\)): 100 milliamperes (mA) (Engineered for low-current signal pathways).Maximum Power Dissipation (\(P_{D}\)): 150 milliwatts (mW) at an ambient temperature of 25°C (Requires structural layout thermal stability).Forward Current Transfer Ratio (\(h_{FE}\) / DC Current Gain): Typically ranges between 30 to 90 when measured at a baseline collector current (\(I_{C}\)) of 10mA.Package Configuration: Hermetically sealed, 3-lead internal metal-can layout (often utilizing the legacy TO-5 or custom Western Electric long-lead low-profile base footprint to eliminate atmospheric moisture contamination).📞 Real-World Historical ApplicationsWithin the context of the AT&T Bell System infrastructure, the 138A served as a foundational active switching and logic element:Electromechanical Central Office Switching Systems: It was deployed inside the peripheral electronic control frames of the No. 5 Crossbar Switching Systems and early experimental Electronic Switching Systems (ESS). It handled the underlying low-voltage logic routing needed to track, translate, and pass along incoming telephone dialing pulses.Bell System 138A Type Telephone & Apparatus Test Units: The transistor was highly integrated into custom testing hardware, line analyzers, and diagnostic tool arrays—such as the official Bell System 138A Telephone / Apparatus Test Module. Field engineers used these specialized diagnostic rigs to measure line resistance, verify signal fidelity, and calibrate analog trunk lines in central offices.Carrier Terminal Multiplexing Equipment: It acted as a low-power pre-amplifier and switching gate within regional multi-channel analog telephone carrier networks, amplifying audio signals before they were modulated onto long-distance transmission lines. (3000PCS IN OUR STOCK)
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