User's Manual

KAIROS User Manual - version 1.3
Radio Activity S.r.l. 12/11/2014 23 / 41
3.3.5.1 Digital I/O
The I/O output pins (PWR_GOOD, M_1, M_2, PTT_OUT_conn, I/O_OUT_1, ALR_OUT, FAN,
OUT_1+1_MNG_CONN) are open collector type able to switch up to 20mA/40Vdc. A 470 Ohm resistor
limits the maximum current and a 47K resistor refers the output to the internal 3.3V.
The I/O input pins (REMOTE_OFF, E_1, E_2, I/O_IN_2, I/O_IN_3, ALR_IN1, ALR_IN2, PPS_IN_CONN) are
internally pull-upped to the 3.3V. A pair of diodes protect the input from voltage below zero. This input
switch on closing it to GND.
The function of such pins are:
REMOTE_OFF : [IN] it is equivalent to push the on/off button in the front of the equipment. When KAIROS
is in on condition, closing this pin to GND for at least 3 seconds produces a switch off condition. When in off
condition, closing this pin to GND for at least 250 milliseconds produce a switch on. See the Power on/off
button description for further details using this pin.
PWR_GOOD : [OUT] it is closed to GND when the equipment is regularly switched on
E_1, E_2 : [IN] closing them to GND advise the equipment that a valid audio signal is incoming from the Line
(like a PTT signal)
M_1, M_2 : [OUT] they are closed to GND when a valid audio signal is sent to the Line (like a SQUELCH
advise)
I/O_IN_2, I/O_IN_3 : [IN] general purpose inputs; they can be used in special applications that need to
acquire external status like: opening cabinet detection, opening site door, main power supply presence
(with external switch)
I/O_OUT_1 : [OUT] general purpose output; it can be used in special applications that need to set an
external device/relays
ALR_IN1, ALR_IN2 : [IN] alarm input; closing them to GND produces an alarm advise to the Supervisor
Centre. Each alarm can be configured via the setup tool; it is possible to define a DMR TXT message or a
SNMP trap for the 0 to 1 transition and for the 1 to 0. Typical application is the open site/cabinet event.
ALR_OUT : [OUT] it is open from GND when the equipment detects an alarm condition. Power off is an
alarm condition.
FAN : [OUT] it is closed to GND when the temperature of the internal RF power amplifier rises above the
threshold (typ 65°C). It can be used to switch on cooling fans in a cabinet.
PTT_OUT_conn : [OUT] it is closed to GND when the transmitter goes on air. It is possible to insert a pre-
time to allow the right switching on time to an external RF power amplifier.
PPS_IN_CONN : [IN/OUT] this pin supports an external PPS signal or can share the internal PPS (from GPS
receiver or from the PTP or from other sourced synch). As described previously, a bus connection between
different co-located KAIROS realizes a multiple GPS reception with automatic backup. This pin can also be