Robot 300

This model was produced using storage tube techniques and is believed
to have been the first commercially available scan converter. Another
first for this model was the ability to view the received picture on a
fast-scan monitor.

The incoming SSTV picture is processed and stored on a silicon target
storage tube, it is then electrically read out and reprocessed into a
fast-scan picture for viewing on a monitor. The transmit picture is
snatched from a fast-scan source, processed and stored in the tube,
from where it is again electrically read and processed into a
slow-scan picture for transmission.

The facilities available with this unit are be comparable with today's
generation of converters, the only real differences being black and
white working only and no internal picture storage. Storage is
achieved by recording on magnetic tape or by photographing the screen.
Once an SSTV picture is stored on tape it can be read back into the
converter for transmission. It is worth remembering that the same
applies to most of the digital converters available, their memories
only store pictures whilst the power is switched on, permanent storage
must be on tape.

As previously mentioned, any picture that is stored in the silicon
tube will eventually fade out, and after a few minutes will have to be
refreshed or replaced. Also, even when new, these tubes, by nature of
their manufacturing process, exhibit small blemishes on the target
which are sometimes seen on the picture.

The specifications for the model 300 include:

* Transmit and receive speeds: 128 lines at 2, 4 or 8 seconds. 256
lines at 4, 8, 17 or 34 seconds - black and white only.

* Video input 1 volt peak-to-peak into 75 ohms.

* Video output 1.4 volts peak-to-peak into 75 ohms.

* SSTV input 20mV to 1V into 10k. Minimum Signal-to-Noise ratio for 
clear picture is 6dB.

* Transmit FM deviation controls set degree of FM swing and centre
value of SSTV picture. Indicators show when limits of swing are
reaches (i.e: 1200Hz for sync and 2300Hz for white).

* Snatch controls to set the required depth of modulation of the
picture from the camera or video source.

* Normal or inverted video transmitted picture.

* Tuning indicator activated by incoming SSTV sync pulses when
correctly tuned.

* Horizontal hold control to allow reception of pictures from
countries using 50Hz
or 60Hz supplies.

* Span and balance controls to set depth of modulation and centre
value of swing of incoming pictures.

* “Hold” facility to freeze an incoming picture on the screen without
updating, to allow viewing or storage.

* Transmit mode can be switched between SSTV mode and voice mode, the
microphone being plugged into a socket on the rear panel.