I.S. INTERCOM
20-278-12
TYPE ABMA4 USER MANUAL
7 OF 21
Issue: 05
trigger does not occur say in PTT action when someone or a machine is whistling or creating noise near
these PSA frequencies.
On detection of the PSA, the unit will wake up the display if asleep and show flashing ticks (
√
) in a PSA loop.
The flashing indicates that the PSA is occurring.
Figure 1: Confirmed PSA Loop
If the ABMA4 sees only an S-line return signal then the V-line will have a cross (X) in the PSA loop and tick
(
√
) in the S-line (see table 2 for more explanation below). The flashing of the ticks (
√
) continue for a small
period after the PSA tone has disappeared to ensure the user sees any PSA changes.
When a PSA event occurs, the Speakers output will go to maximum volume on the first tone of the frequency
pair immediately that it detects a correct PSA frequency. This is so the user has the maximum opportunity to
hear PSA tone at the earliest possible time even before a PSA tone pair has been confirmed by AMBA4.
2. Detection of Speech for Speaker Mute Control
On detection of speech because someone has pressed the SPEAK key and is speaking above the mute
level or squelch levels the speakers are turned on and will remain on for 3 seconds after speech has
stopped. This is to give the speakers some hysteresis so talking does not pop in and out.
3. Detection of Low R-Line Voltage
If the R-line is weak and falls below 6 Volts then a warning message is displayed if in the Generic mode on
the LCD screen. If it remains low, the then unit will fall into a deep sleep to conserve power, all background
functions, and LCD display will stop. This mode should only be used to store units on the store shelves. If in
‘deep-sleep’ the unit can be, awaken up by holding down the ‘Menu’ key for three seconds. If the R-line is
removed, the warning message ‘ZERO’ will be displayed beneath R-line Bar graph.
4. Pressing of SPEAK key
On pressing of the SPEAK key (a press to talk, ‘PTT’ action) the unit will wake up momentary if asleep and
display ‘SPEAK’ in the message text box on the Generic mode of the LCD screen. The ABMA4 will turn off
speakers and turn on the microphone. The unit will return to sleep mode as soon as Speak key is release.
5. Switching between Sleep and Deep Sleep modes
To save battery power when not in use, the ABMA4 goes to sleep when no keys are pressed after 30
seconds. The unit is woken when a PSA occurs (for only 8seconds), SPEAK (for only 1 second) or any of the
menu keys are pressed (30 seconds). The unit is not woken for ‘Call Exchange’ or ‘Call Local’ keys. These
just signal directly to the PSA controller. Sleep consists of turning off the LCD display and backlight. The unit
is still very active doing all other background tasks listed above.
The other mode is ‘Deep Sleep’. This should not occur in the field (see ‘Detection of Low R-Line Voltage’
in previous section above). Deep sleep mode is to save battery shelf life. In an emergency or on the test
bench to confirm operations, you can wake the ABMA4 from deep sleep either by pressing the ‘Menu’ key for
three seconds, adding power to the R-line or pressing ‘SPEAK’ key.
The activation from ‘Deep Sleep’ mode when the ‘SPEAK’ key is pressed (without PSA R-line power) is for
an emergency when you need to speak to other ABMA4 intercoms to attract attention. If the other ABMA4
intercoms have R-line power then the system will work as normal until the unit that has no R-line battery runs
flat. If all other ABMA4 units are in ‘Deep Sleep’ as well, they will only monitor for speech every few seconds,
upon the detection of which they will awake and turn speakers on. Thus in ‘Deep Sleep’ mode you need to
speak for longer than one second before the ABMA4 will open their speakers. This assumes there is enough
battery power in the units, which would be true for the case for a power-outage of a few days or weeks.
