Westinghouse Type KR Installation & Operating Instructions Manual page 44

T Y P E K R CARRI E R SET
order to match oth er s witchboar d equipment. The out­
line dimensions and al so th e dril ling plan for fl ush
and projection mounting are shown by Fig. 1. T he
majori ty of the par ts ar e mounted on a pr inted circuit
board. This board may be readily removed as foll ows :
1 . Remove the two output plugs from the red and
black jacks.
2. Disconnect the receiver input c oaxial cable
connector.
3. Loosen th e two s crews at the top of the board.
4 . Loosen the two screws at the bottom of the
boar d and pull them out as far as the y will extend.
1
5. Pull board down to disen gage the terminal s
and i ft out.
Th e transmitter output filter may be removed by
removing four mounting s crews from the bottom of the
case and disconnectin g the coaxial cabl e.
Fi g . 6. shows the l ocation of major components
such as p otentiometers, j ac k , test points,
transi stors , etc. External
Schematic Diagram are shown by Fig. 2. The num­
b ered termin al s shown as s quares apply to the ex­
t ernal terminals.
P r ovi sions are- made for plugging
Adapter Unit in the r ear of the relaying equipment.
octal socket mar k e d X- 4 on t h e r ear of the s et
accommodates the adapter pl ug. A buck l e type strap
on each side of t h e adapter hol d s the unit in place
after i t has been p lu g ged in. The normal projection
for a rear mounted Voi ce Adapter is 3-inch e s be­
yond that of the relaying equipment. Wh en th e K R
Relaying Unit i s supplied with the adapter, a patch
cord i s avail abl e on s ep ar ate order. This patch cord
plugs into the telephone j acks on the ad apter and p r o­
vides an extension to a convenientl y located terminal
board.
The panel cutout information necessar y for mount­
ing the Sl eet Detector is shown by Fi g. 1 1 . This
unit c on sists of a potentiometer and pushbutton
s witc h mounted on a small panel , itsel f suitabl e for
s witchboard mounting.
For 250-volt operation, s eparate auxiliar y resis­
tors are required, a s shown i n Fig. 8 .
E l ec t r i c a l
Tran smitter
The transmitter is m ade of four main stage s in -
4
crystal s,
connections and the
the Voice
eluding an oscill ator, driver, power amplifier, and an
output filter. In th e oscillator, th e cry stal is op erate d
as a re sonant circuit b etween the collector of one
tran si stor and th e b ase of the oth er. The feedback is
supplied through a capacitor from th e collector of the
s econd tran sistor to th e bas e of the first transi stor.
The frequen c y is independent of vol tage or tempera­
ture changes of th e tran sistors. Thus the frequency
stability is the stability of the crystal .
The input to the driver stage Q- 1 0 is controll ed
by potentiometer, R-42 which al so control s the trans­
mitter power output. In H ZM relaying CARRIER STOP
provides about + 40 volt s for blocking. Thi s is ap­
plied to Q- 10 through T-6. Diode C R- 5 prevents dam­
age to the transi stor when this positive vol tage is ap­
plied to the coll ector. For C ARRIER START ( wh e n
in t h e blocked position) a small positive vol tage i s
applied t o the collector of Q- 10 b y means of bleeder
resistors R-67 and R-6 8 .
T h e p ower amplifier consists o f t w o transistors
Q- 12 and Q- 1 5, which are operated as class B ampli­
fiers in push-pull . Resi stors R-52 and R- 55 are for
s tabil ization.
Th e output transformer,
cabl e s of 50 to 70 ohm s .
Resistor R-66 tends to k eep t h e source impedence
constant to p ermit proper tuning of the output filter.
The output filter consists of coils L- 1 and L-2,
capacitors C- 1 9 through C-22. The f ilter is tunabl e ,
and i s provided t o attenuate harmonic s and other
spurious outputs. It shoul d be noted that the filter
contains no shunt elements, resulting in a reverse
impedance free of "across th e lin e " resonances.
Receiver
The receiver i s a sup erheterodyne in ord er to
obtain constant sel ectivity regar dl ess of the channel
frequency. (See Fi g. 1 4 . ) The major stages include
an input filter, at tenuator,
filters, IF amplifi ers, detector and a D- C power out­
p ut stage.
The input filter prevents undesired signals from
producing the fr equency.
IF
The receiver sensitivity is adjusted by means of
the continuously variable input control
T-7, matches coaxial
oscill ator, mixer, IF
and by
R- 1