TELE-TECH & - AmericanRadioHistory.Com

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HEREIT1F!
A NEW Plug -In Trimmer
for Printed Circuit Boards
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ELECTRONIC
Vignettes
Germanium Milestones
to general belief, ger-
CONTRARY manium has been used in electronic
circuits long before the advent
of the transistor. As long ago as
1923, Dr. Charles G. Smith of Raytheon
applied for a patent on the use
of germanium as a rectifying element.
This patent, No. 1,679,448 -
Electrical - Current Modification,
awarded in 1928, is described below.
The invention involves the use of
a resistance element whose resistance
changes rapidly in response to temperature
changes. The temperature
coefficient may be either positive or
negative and preferably has both a
positive and negative range so that
it may be changed from positive to
negative by a relatively slight change
of temperature. Germanium is such
an element. See Fig. 3.
The ERIE 3192 Plug -In Trimmer keeps pace with current
design trends while maintaining the qualities for which ERIE
Trimmers have long been notable -fidelity to specifications,
rugged stability, and straight -line capacity change throughout
the total range. All the features of the popular Style 557 are
embodied in this new trimmer.
Note these features:
Designed specifically for Printed Circuit Boards
Ideal for critical vibration applications
Compact and convenient for application in miniaturized
circuits
Available with zero or negative temperature characteristics
Custom built assemblies to suit the customer's needs
ERIE has been a leader since 1940 in the manufacture of
Printed Circuits. The ERIE Printed Circuit Board shown
above has these special features:
Approved by Underwriters' Laboratories
Unusually rigid construction
Boards do not come in contact with acids of any type
while being produced
Custom designed to meet your requirements
Write for Engineering Bulletin on the ERIE 3192 Plug -In Trimmer
and ERIE Printed Circuit Boards.
ERIE ELECTRONICS DIVISION
ERIE
RESISTOR CORPORATION
Mom Offices and Factories ERIE, PA.
Manufacturing Subsidiaries
HOLLY SPRINGS, MISSISSIPPI LONDON, ENGLAND TRENTON, ONTARIO
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In rectifying alternating current,
the temperature of the resistance element
is varied in synchronism with
an alternating current so that it offers
greater resistance to the passage
of the ac in one direction than in the
other. (Greater resistance during the
positive half -cycle than during the
negative, or vice versa.) The tern -
perature may be varied directly by
the ac or by an auxiliary source of
heat whose frequency of application
is synchronized with the ac.
A typical circuit showing the use
of germanium as a rectifying element
is seen in Fig. 2. The battery
will oppose alternate half -cycles of
the current and aid the other half -
cycles. The resultant of the individual
currents produced by the battery
(B) and the trasformer (T), in
the absence of the germanium element
(G), is represented by curve H
of Fig. 2a. By properly coordinating
the circuit elements, the relatively
large half -cycles of current (positive
cycles of curve H) may be caused to
heat the resistance element G to the
range where its coefficient is negative.
Resultant current is curve D.
44 For product information, use inquiry cord on pages 209 -210
Tele -Tech & ELECTRONIC INDUSTRIES June 1956