THIS INFORMATION IS SUPPLIED IN GOOD FAITH. GEMTEK
SYSTEMS ACCEPTS NO RESPONSIBILITY
FOR ANY ERRORS IN THIS INFORMATION WHAT SO EVER.
OBIT ALARM RE-ALIGNMENT. (only if
required).
(Note: The following information is for the alignment of RE001,GEM076
and original
"Capital Radio" PCB's. GEM076 PCB's can be configured to work in RE001
mode if RL5.
is ommitted.)
Before the following procedure is carried out, check that the audio
level out of
your receiving equipment is being applied to the card at the correct
level. Record
start tones before clip feeds should be received and distributed at
-10dBu. A
quality recording of the double tone burst that IS the
Obit alarm signal will
be required. This can be recorded from your receiver on the day of the
week on
which IRN [ITN (Radio) Ltd.] do their "engineering network test".
1. Set up power supply to be ±12 Volts ±0.5 volts. Ensure
that the 0V line has a
good ground.
2. Switch supply on, but do not connect the audio input. After
approximately 2
minutes the line fail relay will operate and LED 4 will illuminate.
Apply an audio
source and then reset RL4 by grounding the reset input.
3. Apply 1kHz tone at -12dBu to the audio input and connect an
oscilloscope to
TP3. Adjust VR1 so that the audio waveform seen on TP3 is on the verge
of
clipping. Disconnect tone if relay RL1 has activated and wait for relay
RL1 to
deactivate (RE001 mode).
4. Connect oscilloscope to TP4. Apply signal from SMS receiver to input
and wait
for record start tone that precedes clip feeds from IRN [ITN (Radio)
Ltd]. It is
important that this source of tone is used to align the 1kHz filter.
Adjust VR2
so that the waveform on TP4 is peaked and symmetrical. The "bing tone"
can also
be used for this, but the trimmer only requires a small adjustment
either side of
the peak to loose the signal completely, so the twenty second record
start tone
is easier.
5. Having completed adjustments 3 & 4 above, leave card to check
that RL1
energises and LD1 illuminates (or pulses in GEM076 mode) within twenty
seconds from
the beginning of a record tone received from the receiver, starting.
6. If step 5 above proves satisfactory, monitor receiver audio, and
when feed is
finished, check that record start relay de-energises within thirty
seconds (RE001
mode) or RL5 pulses on (GEM076 mode).
7. Set up your recorded source of the "obit alarm tones" so that its
replay level
can be varied and verified. First check that the card responds at
-10dBu actual
replay level. Obit 1 (RL2) should pulse on, record start (RL1) should
energise and
Obit 2 (RL3) should latch. At this point, if RL3 has latched do not
worry about
resetting it. To fine tune the tone decoder, adjust VR3 finely in both
directions
while simultaneously reducing the replay level of the tape machine.
Leave about
5 seconds between each double burst of tones and check that RL2 &
LED2 energise
each time. It should be found that with a little effort, the decoder
can be made
to respond to tones at less than -40dBu when properly lined up. Tones
would
normally be sent by IRN [ITN (Radio) Ltd.,at -10dBu.
8. Remove input signal and ensure that the record start relay
de-energises. Apply
a ground to the reset input, Obit 2 (RL3) should now de-energise.
Trevor K.P. Gosling. (07/04/97)
GEMTEK SYSTEMS.