Tait TM8000 Series

TM8100 Mobile Radio Service Manual Circuit Descriptions 75
May 2004 © Tait Electronics Limited
Battery Power Sense For the battery-power-sense option the link LK1 is required to connect
+13
V8 BATT of the power connector to the power-up circuitry. With this
option, when a 13.8 V supply is connected to the radio, the radio enters
the programmed power-on mode. The
ON/OFF key can then be used to
turn the radio on and off. This option has the disadvantage that the radio
still draws about 28 mA after being switched off using the
ON/OFF key.
The reason is that the radio enters the stand-by mode and does not shut
down completely.
Auxiliary Power Sense With the auxiliary power-sense option the digital input line AUX GPI3 of
the auxiliary connector is used to power up and power down the radio.
The link LK2 is required to connect the line to the power-up circuitry.
The line is active high; it is on when the level exceeds 2.6 V and off
when the level falls below 0.7 V; the line tolerates maximum inputs equal
to the radio supply voltage. When the line becomes active, the radio
enters the programmed power-on mode. The
ON/OFF key can then be
used to switch the radio on and off. With the radio off and the line
active, the radio draws about 28 mA. When the line becomes inactive,
the radio is shut down completely regardless of whether it was on or in
stand-by mode. With the line inactive the radio draws less than 1 mA.
In a vehicle installation this avoids flattening the battery when the
ignition key is off.
Internal-options
Power Sense
The internal-options power-sense option is similar to the auxiliary
power-sense option, except that the
IOP GPIO7 line of the internal options
connector is used. The link LK4 is required to connect the line to the
power-up circuitry. This line is also active high; it is on when the level
exceeds 2.6 V and off when the level falls below 0.7 V; the line tolerates
maximum inputs of 5 V. The behaviour of the
ON/OFF key is the same as
with the auxiliary power-sense option.
No Power Sense If no power-sense option is selected, the radio can only be powered up
and powered down by means of the
ON/OFF key. For this option the links
LK1, LK2 and LK4 must be removed. The advantage of this option over
the battery power-sense option is that the radio draws less than 1 mA
when it is switched off.
Emergency
Power Sense
For the emergency power-sense option the AUX GPI2 line of the auxiliary
connector is used. Externally, this line is typically connected to a hidden
switch. Internally, the link LK3 is required to connect the line to the
power-up circuitry. The line is active low and has an internal pull-up
resistor to the external supply voltage. The line is on when the level falls
below 0.7 V. When the line becomes active, as when the hidden switch
is pressed for two seconds, the radio enters the emergency mode. This
mode can also be activated by making an emergency call or by pressing
a key that has been programmed appropriately. The concealed
microphone is typically fitted when the emergency power-sense option
is selected.