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Rectifiers
Rectifiers convert alternating into direct voltage, they have
hardly no influence on the level of the voltage. They have four
pins: two for the input voltage (a.c. voltage) and two for the
output voltage (d.c. voltage). The pins for the output voltage
are polarized. The pin connections are printed on the housing.
Transistors
Transistors are current amplifiers which convert low signals
into stronger ones. They have three contacts. As they are
polarized, they have to be mounted in a certain direction.
BC-Types have a housing in form of a half cylinder (SOT-
housing). The cross section is shown in the PCB Layout which
determines the mounting orientation.
The BD types have a flat housing (TO-housing) with the type
designation printed on the front side. The metallic rear is
unlabelled, on the PCB layout the rear is marked by a thick line.
Integrated circuits (ICs)
Depending on the type, ICs fulfil various tasks. They are
polarized and therefore have to be mounted in a certain
direction. The most common housing form is the so-called
"DIL"-housing, from which 4, 6, 8, 14, 16, 18 or more "legs"
(pins) are arranged along the long sides. The mounting
orientation is shown by a semicircular or circular marking at the
end of the housing, which is also shown on the PCB layout.
ICs are sensitive to damage during soldering (heat,
electrostatic charging). For that reason in the place of the ICs
IC sockets are soldered in, in which the ICs are inserted later.
The mounting orientation of the sockets is preset as well. The
markings on the PCB, the socket and the IC must lie on top of
each other after mounting.
Page 40
PZS-3
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