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UMW
Vol. 13, No. 5
COMPLETE ELECTRONIC SERVICING INFORM
radio • tv • hi-fi
ATIOI
November, 1961
G- E SONIC REMOTE CONTROL SYSTEM I
The RF type remote control sys-
tem was described in Vol. 12, No. 2
through Vol.
13, No.
1 issues of
TECHNI-TALK. This system was
initially used in the General Electric
"U4" and " M5" lines of receivers and
was continued in a portion of the
"M6" line.
Sonic Remote Control System
A new type remote system was also
used in some " M6" receivers. This
new system has but two function
buttons on a new style remote hand
unit. The electrical differences be-
tween the two systems are extensive
as the
former
system
engaged
a
modulated RF carrier, while the lat-
ter is considered a super-sonic car-
rier system. This new control system
will be discussed in detail and will
be referred to as the Sonic Remote
Control
System.
The
units which
make up this system are pictured
in Fig. 1.
Fig. 1
Units used in General Electric
Sonic Remote Control System
The sonic system carrier operates
in the range of 40KC with signals
produced by a transistorized hand
unit. This system is extremely noise
resistant to
provide
immunity
to
audible noises produced in the area
of operation.
While the transmitter unit has
only two operational
buttons,
the
operator is still able to perform all
the functions of the RF models, that
is; turn the TV receiver off or
-
on
remotely, change channels and raise
or lower the audio volume level to
suit his listening pleasure. This lat-
ter function is performed by a step
type relay which provides a normal
position, high level, mute and low
sound level.
The channel change operation pro-
vides one position where the TV re-
ceiver is turned off. This is normally
set at the 13th position of the tuner
except on those models where UHF
has been included. Models factory
shipped with UHF have the off posi-
tion set at the channel 9 position.
This is easily changed by moving
the
nylon contactor
on
the OFF
selector disk, located at the rear of
the tuner as shown in Fig. 2, to an
unused channel position and then
programming this channel with the
front tuning knob as is outlined in
the operating instructions.
OFF- SELECTOR
DISK
(/ y.
OFF- BUTTON ....•""«.<-
55 55
2
Off position selector disk
Fig.
The transmitter hand unit for the
Sonic Remote System is a transistor-
ized
super-sonic
oscillator
circuit.
This unit is capable of producing two
super-sonic signals for activating re-
ceiver function relays. No audible
sound is produced by this system as
there is no modulation added to the
carrier.
The new sonic remote transmitter
is a simplified transistorized oscil-
lator circuit producing two tones. The
higher of these tones is a 41KC sig-
nal which operates the channel se-
lect and remote off relay. The lower
tone is 39KC and is used to key a
stepping relay to provide four steps
of audio level change.
The simplicity of the circuit is ev-
ident when you view the schematic
of the transmitter, Fig. 3. The cir-
cuitry consists of an oscillator coil
L751 which is tuned to the upper fre-
quency of 41KC. When power is ap-
plied, switch S752 is closed complet-
ing the ground or common side of
the line. The double pole switch is
used to insure that power is applied
to the circuitry after the circuit com-
ponents
are
switched
to
prevent
transistor failure. The tank coil is
tuned by C753, a 1350uuf capacitor,
and is loaded by R754. The oscillator
circuit of TR751 is a base biased
NPN type transistor:
Pressing S751 shunts C754 into
the circuit and lowers the frequency
to 39.0KC. The output of the oscil-
lator is fed to a PNP buffer-amplifier
circuit TR752 which has its output
fed to L752. This coil placed across
the transducer has 2 modes of opera-
tion which when properly set provide
the desired amplification for either
frequency. This output circuit has
the signal fed between the base and
emitter.
R751, the 680 ohm resistor in the
emitter
of
TR751,
acts
as
a
Continued on Page 9
8753
y
47K
IR 751
26306
y
475
C754
NPN
c
o
'
q
s
7
c
5
3 I F"
5°-530
s
o
n
tl
v e
STEPPING
.1._
lerAvL
-
1
1
7*;41
3309 _1'
35
°
I
3V
3.9v
C751
1022
R75,
680
C752
2
.911
5752
ON- 011
CHANNEL
SELECT
C755
24090
R752
15fl
TR 752
PNP
28319
AMP
33
VOLTAGES TAKEN WITH a vTvM
ALj.f
6ATc
TYPES
28
271321
1111100V/V9
K
V
C
C
Lk
3
I
sz
73V
HAn
Fig. 3
Schematic diagram of ceramic transducer transmitter
used in Sonic Remote Control System
A75,
CERAMIC
TRANS-
DUCER
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