TM8100/TM8200 Service Manual Circuit Descriptions 89
© Tait Electronics Limited November 2007
Battery Power
Sense
With this option, link LK1 connects +13V8 BATT of the power connector to
the power-up circuitry. With this option, when a 13.8V supply is connected
to the radio, the radio enters the programmed power-on mode. The
ON/OFF
key can then be used to switch the radio on and off. This option has the
disadvantage that the radio still draws about 50mA 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
(Ignition Sense)
This option uses the digital input line AUX GPI3 of the auxiliary connector to
power the radio up and down. 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 2.6V and off when the level falls below 0.7V; 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 50mA. 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 1mA.
In a vehicle installation this avoids flattening the battery when the ignition
key is off.
Internal-Options
Power Sense
This option is similar to the auxiliary power-sense option, except that the
IOP GPIO7 line of the internal options connector is used. Link LK4 is required
to connect the line to the power-up circuitry. This line is active high; it is
on when the level exceeds 2.6V and off when the level falls below 0.7V;
the line tolerates maximum inputs of 5V. 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 1mA when it is
switched off.
Emergency
Power Sense
This option uses the AUX GPI2 line of the auxiliary connector. Externally, this
line is typically connected to a hidden switch. Internally, 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 0.7V. When the line becomes active (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.
Operation in
Emergency Mode
If the radio is off when the emergency mode is activated, the radio is
powered up but the display on the control head is not switched on. If the
radio is on when the mode is activated, the display is frozen. In the latter
case, if the
ON/OFF key is pressed, the display is switched off but the radio
remains in the emergency mode. While in this mode the radio cycles
between transmit and receive. To exit the emergency mode, the
ON/OFF key
needs to be pressed again.
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