Service manual

DATA INTERFACE DESCRIPTION
A-4
April 2001
Part No. 001-9800-203
EMERGENCY - Asserting this signal causes the
radio to act as if the “Emergency” switch has been
pressed.
EXT SERV REQ - Normally, all input lines are
polled on a regular basis (approximately every 40 ms)
to detect changes. Under certain conditions, such as to
improve response time or to make sure a transition is
not missed, it is desirable to force a check of the input
lines. This is done by asserting the EXT SERV REQ
line (applying a high to low transition). This line is a
main microprocessor interrupt that when asserted,
causes the radio software to immediately check and
then process any input state changes on In 2 and In 3.
HORN - When asserted, this signal initiates a horn
honk event (see Section 3.5.10). The alert sounds for
the fixed or programmed number of cycles and then
returns to the disabled state. For the alert to sound
again, this signal must be released and re-asserted.
PTT - When this signal is asserted, it is treated as a
normal microphone (voice) PTT signal. While it is
asserted, DATA PTT (and DATA PTT REVERT) are
inhibited. The high tier Emergency function takes
precedence over this PTT signal. Data and voice group
hunting are inhibited, so access occurs on the current
revert system and group.
PTT INHIBIT - This signal prevents any action from
being taken in response to user or control unit PTT
signals. DATA PTT operation is not affected when this
line is asserted.
A.3.4 OUTPUT FUNCTIONS
The following are descriptions of the output func-
tions listed in Table A-2.
ACCESSORY OPTION - This is the output signal
for the option select function that is toggled by an
option switch or the menu OPTION parameter (see
Section 3.5.11). The asserted condition = option
enabled.
AUDIO ENABLE - When this output is asserted,
either microphone or speaker audio is enabled,
depending on whether the transmit or receive mode is
active.
BUSY - When transmitting, the asserted condition
indicates that an attempt to transmit failed because the
channel or system was busy. When receiving, it indi-
cates that the current channel or system/group is busy.
CALL GUARD - If the conventional group is
programmed for Call Guard squelch, the asserted
condition indicates that the correct Call Guard code is
being detected. If the conventional group is not
programmed for Call Guard squelch, this line is
asserted when unsquelched (audio enabled) and
released when squelched.
CALL INDICATOR - The asserted condition indi-
cates that the call indicator is active.
CLEAR TO SEND - The asserted condition indicates
that the radio has completed all channel access activity
and is ready for the external device to begin sending
audio or data.
COMPAND - The asserted condition indicates that
companding should be activated for the transmit and
receive modes.
DATA CTS - The asserted condition indicates that the
radio has completed all channel access activity on a
data group/channel and is ready for the external device
to begin sending data.
ENCRYPT - The asserted condition indicates that all
transmitted audio should be encrypted. This is
controlled with a combination of group programming
and a menu parameter or option switch (see Section
3.5.7).
MONITOR HANGER - This output mirrors the
“logical” microphone hanger status. It is asserted
when an on-hook condition is indicated by the local
microphone and also all control units (if applicable).
PTT PRESSED - The asserted condition indicates
that the user PTT switch is pressed in at least one loca-
tion such as the local microphone or a control unit.
RSSI - The asserted condition indicates a “fast” carrier
detect condition. On early models, it uses the received
signal strength indication (RSSI), and on later models
with the faster noise squelch circuit, it uses the squelch
circuit output.