4
Exposure to radio frequency energy and potential harmful effects
The transmitter operates at an extremely low power of 5 milliwatts or less, (somewhat less than a
typical mobile phone) however you should be aware that the effects of radio frequency energy on the
human body are not fully known at this time and exposure should be minimised wherever possible. As
mentioned above, if you can keep the transmitter away from your body, so much the better.
Rechargeable batteries
You may find it more economical to use rechargeable batteries in the transmitter. Kenton recommend
that you have two rechargeable batteries, one inside the transmitter, and one on charge. Kenton can
supply high capacity rechargeable batteries and chargers suitable for use with the
MidiStream
transmitter.
The rechargeable batteries we supply have a capacity of 250mAH (most are 150mAH) which means
that you can operate the transmitter for about 5 hours continuously on one charge. Contact us for more
details.
Power save mode
If the system is likely to be used in a situation where there are long idle times between MIDI messages
(many minutes), you can enable power save mode in the transmitter to increase battery life. To control
power save mode, you need to send one of the following SysEx messages to the transmitter :
To enable power save mode and set timeout, send
F0 00 20 13 0B 00 00
TT
F7
To disable power save mode (always on), send
F0 00 20 13 0B 00 00 00 F7
Where the strings given above are in hexadecimal and
TT
is the time in minutes before the unit turns
itself off – values 1 to 127 minutes are valid times until turn off, and 0 means the unit stays on all the
time.
TT
must never be more than 127 decimal (7Fh). For example F0 00 20 13 0B 00 00 3C F7 will
set the timeout to 60 minutes (3C is the hexadecimal representation of 60). See the next page for more
examples and a decimal to hex conversion chart. Any setting is stored in non-volatile memory, factory
default value is ‘always on’)
When power save mode is enabled, the transmitter will stop transmitting RF (radio frequency) if no
MIDI message has been received for a pre-determined time (set as
TT
above). You will know that the
transmitter has stopped because the two LEDs, RF-A and RF-B on the receiver, will go out and the led
on the transmitter unit will blink briefly every two seconds. As soon as a new MIDI message is received
the transmitter will turn back on, but be aware that the turn-on and re-synchronisation process takes a
few milliseconds so the first message will be delayed very slightly, although probably not noticeably.
Although the unit uses less power when the transmitter is stopped, it doesn’t reduce power
consumption to zero. Typically power consumption is reduced to one third of normal when the
transmitter RF section is shut down. Power consumption is
only
reduced when the timeout has
occurred and the RF section has shut down, otherwise power consumption is normal.
For the unit to shut down the transmitter RF section in power save mode, it must receive
no MIDI
messages of any kind
during the timeout period. If your MIDI instrument constantly sends active
sensing messages then the transmitter RF section will never shut down and no power will be saved.
Uses for the MidiStream system
Although the
MidiStream
system was originally designed with instruments such as the AX-1 in mind,
many other uses have been suggested since. The main other instruments are wind controllers such as
the WX-5 and MIDI accordions. As well as those uses,
MidiStream
can be used in theatres or other
venues to couple a front-of-house MIDI sound or lighting desk to slave units on stage.
MIDI throughput
MidiStream
has a very low latency and high MIDI throughput. It handles all MIDI messages including
Clock and SysEx messages, however, try to avoid very large SysEx dumps (1k or more). If you need to
send very large dumps, try to split them up into blocks with a few milliseconds between each block.
MIDIOX can do this. MIDIOX is an extremely useful utility and you can download it for free from
www.midiox.com
