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Schaltungsbeschreibung / Circuit Description

AMPLOCK

V/I

VCO

Level

Detector 1

Level

Detector 2

Frequen cy

Counter

Frequen cy

Synt

hesizer

To Audio
Processing

AGC

FM in

C-PUMP

IC1100 STV0056A

SDA

SCL

{

C Bus

46 ,41

49,38

42,26

47,39

PLL

Filter

comes blue. With the "green" key on the local keyboard it is possible
to change the background to green.
Pin 21:
AV switching voltage input for evaluation of the switching voltage on pin
8 of the decoder socket. If "AV IN1" is at high level the video signal is
fed back to the receiver via the connected descrambler.
Pin 22:
AV switching voltage input for evaluation of the switching voltage on pin
8 of the VCR socket. At high level "AV IN 2" the VCR signal is looped
through to the TV receiver (matrix).
Pin 23:
Connection to the local "DOWN" (programme down) key in the SAT
Mouse.
Pin 24:
Control voltage U

AFC

for SAT Tuner frequency control.

Pin 48, 49:
System data and clock lead to control the tuner, IC1100,IC1330,
CIC1420 (I

C-bus).

Pin 37:
Enable signal CS

OSD

(Chip Select OSD) for the OSD Controller IC1330.

Pin 38:
RGB/TV switching voltage for changing over the Scart sockets (ma-
trix). When the RGB/TV switching voltage is at "High", CT1270,
CT1276 switch the TV receiver to RGB mode.
Pin 39:
AV 3 switching voltage to pin 8 of the TV-socket.
Pin 40/41:
Serial clock and data lead to drive clock CIC1120 (only provided)

2.2 Non Volatile Memory
NVM CIC1420 is a serial EEPROM and contains all factory and user
programmable data to configure the receiver (channel table, deviation,
polarity etc.).

3. Tuner

All functions within the tuner are controlled from IC1400 via I

C Bus.

The IF signals from the LNC, in the range 950MHz to 2150MHz, are
supplied to the aerial input.
The LNC-input is AC-coupled into a variable amplifier whose gain is
adjusted automatically by the AGC to ensure a constant level at the
input to the FM Demodulator. At the output contact 4 of the tuner the
baseband signal is available together with the 25Hz energy dispersal
waveform signal.
To improve the picture quality resulting from a noisy transmitter signal
a "threshold" circuit can be activated in the tuner via the menu.

4. Audio Path

Note to the block circuit diagram Audio Demodulator:
Where two pin numbers are given two circuits exist, one for each stereo
channel. The first number is for the Right channel.

Audio Demodulator Block Diagram

The FM audio demodulator is of the Phase Locked Loop (PLL) type.

FM signals in the tuner Baseband Video signal are filtered by CC1014,
L1014, CC1016, L1016, L1019, CC1017, CR1017, L1017 which
removes unwanted Video components from FM in.

It is important that the drive level of the signals being demodulated is
fixed so that the output amplitude from the demodulator can be
predicted. To help achieve this the input signal passes through a gain
controlled amplifier G1, whose gain is set by one of two level detectors.
When a signal is first selected Level Detector 1, which senses the
combined FM signal amplitude, is used to set G1 to an approximately
correct gain. Once PLL lock has been reached Level Detector 2 is used
which accurately monitors the actual signal level within the working PLL.

When a new audio carrier is being selected the PLL must be tuned to the new
frequency. To do this S1 is closed and the Voltage Controlled Oscillator
(VCO) is adjusted by means of the Frequency Synthesiser. The VCO
frequency is read by the Frequency Counter. Once the VCO is on frequency
S1 is opened and the VCO locks onto the incoming carrier of the same
frequency. The control loop feedback signal at the input of G2 carries the FM
modulation. The gain of G2 can be controlled to handle different FM
deviations. Loop stability is maintained by the PLL filter.
Control of all functions in the Demodulator is via the I

C bus (SDA, SCL)

from IC1400.

Note to the block diagram Audio Processing:
Where two pin numbers are given two circuits exist, one for each stereo
channel. The first number is for the Right channel.

Audio Processing Block Diagram

4.1 Noise Reduction System (NRS)
The NRS consists of a peak level detector and a controlled low pass
filter. Audio for each channel to its peak detector is band limited by an
external band-pass filter, and centred on the transistors CT1073,
CT1081.

The output of each peak detector is a voltage stored in its NRS time
constant. This is a dc level which will vary with the amplitude of the
audio channel signal and is used to control the frequency response of
its NRS filter via a variable transconductance amplifier.

Switch S3 is used to select the NRS system.

4.2 Passive Deemphasis
S4 is used to select the type of passive deemphasis that is applied to
each audio channel. The options are set by external networks and are
J17, and 75

S. 50

S is obtained by adding an internal resistor in

parallel with the 75

S network.

For PANDA operation NRS and 75

S are used together.

5. Video Noise Filter

The baseband signal from the tuner is passed through a 10MHz low-
pass filter consisting of L1007, CC1011, CC1007, and CC1008, to
remove unwanted noise before it is taken to the Video Processor
IC1100-(20) for further processing.

N RS

Passi v e
A udi o
D e-em phasi s

6dB

28,27

25,24

51,52

2,54

3,53

1,55

33,34

48,40

14,12

6,10

22,21

To
TV

From

To
VCR

SCART

75
u

J1
7

-e

asi
s

-e

asi
s

Peak

D etector

B and-Pass

Fi l ter

ilt
er

DEC

SCART

DEC

From

Vo l

SCL

SD A

{

C B us

IC1100

ST V 00 56A

VCR

SCART

Video Processing Block Diagram

6. Video Processing

6.1 Video Gain Control in IC1100
Baseband Video from the Tuner section is ac coupled into a controlled
amplifier whose gain can be set to give the desired Video amplitude.

6.2 Video Inverter
The polarity of the video signal can be set by the invert switch so that,
for instance, C band reception can be achieved.
After the invert selector switch this signal forms the BASEBAND input
to the Video Matrix and PAL De-emphasis.

6.3 PAL Deemphasis
The baseband signal is applied to the non-inverting input of an
amplifier which has a PAL De-emphasis network in its negative
feedback loop.

After the de-emphasis the PAL signal is band limited by the 5MHz Low-
pass Filter. In the following, the signal is ac coupled into the clamp to
remove the 25Hz energy dispersal waveform. The resulting signal is
the NORMAL video input to the Video Matrix.

6.4 Video Matrix IC1100
This is a cross wire matrix of switches which can select any one of the
Video sources and make it available to each of the three outputs. In
addition to the SAT-video signals described above video is also fed to
the matrix from the VCR and DEC sockets, each signal being clamped
to the same level to avoid switching disturbances. All Video Matrix,
Invert and Video Gain are controlled via I

C-bus. The output signal from

the matrix is sent to the TV, VCR and DEC socket.
Megalogic control is possible via contact 10 of the SCART sockets.
With the red key on the remote control handset it is possible to call up the
signal sources on the AV sockets (A1 Dec, A2 VCR, SAT-TV).

6.4.1 TV Socket
By a "High" level switching voltage U

AV OUT 3

CIC1400-(39), the 12V

switching voltage is fed through CT1254, CT1250 to the TV Scart
socket, contact 8, and consequently the TV receiver is switched to the
AV mode.
The OSD signal is taken from the output IC1330-(8) via CT1260 to the
TV socket (contact 19).

6.4.2 VCR Socket
The audio and video signals to be recorded are provided on contact 1/6 and
19 respectively of the VCR socket.
On VCR playback the IC1100 applies the audio/video signal to the TV socket
via the switching voltage from the VCR socket - contact 8, U

AVIN 2

CIC1400-(22).

6.4.3 Decoder Socket
On Decoder operation, the switching voltage from the DEC socket -
contact 8, U

AV IN 1

CIC1400-(21) - feeds the descrambled audio/video

signal to the TV and VCR socket.
On RGB operation, the RGB switching voltage from the DEC socket -
contact 16 connects the RGB signal via CT1276 to the TV socket. The
TV receiver changes to RGB mode.
If a switching voltage is simultaneously applied to contact 8 of the VCR
socket, the switching voltage U

RGB TV

is fed out from CIC1400-(38) and

the RGB switching voltage at the TV socket is switched off by CT1270.
VCR priority operation: the VCR-signal is only fed through the video matrix
IC1100 to contact 19 of the TV socket.

7. OSD and Synchronisation

The video signal "V

TV OUT

" via CT1365 is also used as the feed for the

On Screen Display (OSD) insertion circuit which adds menus and
status information to the video signal to be displayed on the TV. The
sync tips of the video signal "V

TV OUT

" are clamped at a predetermined

level by CT1350.
The presence of a standard sync is signalled from IC1330-(14) to
CIC1400 via the "U

EXO SYNC.

" lead.

In the absence of a valid sync signal, IC1330 is instructed to generate
its own sync signal so that the screen background becomes blue and
the OSD can still be used.

All control of the OSD is effected via the SDA, SCL and CS OSD leads.

PA L

De-emphasis

Low Pass

Filter

Clamp

PAL

BASEBAND

NORMAL

DECODER

VCR

-1