I.S. INTERCOM
5 OF 6
20-320-12
TYPE ABMA3-1 USER MANUAL
Issue: 03
2. OPERATIONAL DESCRIPTION
Pre-start Alarm (PSA)
The unit continuously detects for a PSA paired tone signal on the V-line and broadcasts it through the
speaker.
Detection of Speech for Speaker Mute Control
On detection of speech from another unit, due to someone having pressed the SPEAK key and is speaking
above the mute level or squelch levels, the speakers are turned on.
SPEAK key
Pressing of the SPEAK key (a press to talk, ‘PTT’ action) the ABMA3-1 will turn off speakers and turn on the
microphone. The unit will return to normal mode as soon as Speak key is release.
CALL LOCAL key
Pressing the CALL LOCAL key will cause the S Line to be pulled down signalling the PSA Controller to send
out a tone indicating attention. The S line normally sits at a DC voltage level between the system supply
voltage and the supply voltage less one volt. If the DC voltage level on the S line with respect to the R line is
changed to a value greater than six volts, the pre-start alarm controller will issue a local call tone (1200Hz)
for as long as the local call button is pressed. A CALL LOCAL tone can be requested from any intercom or
BMA along the length of the conveyor. The CALL LOCAL tone is used to attract attention of personnel along
the conveyor.
CALL EXCHANGE key
Pressing the CALL EXCHANGE key will request a CALL EXCHANGE tone from the controller, by changing
the DC level of the V line. The V line normally sits at a DC voltage level between the system supply voltage
and the supply voltage minus one volt. If the DC voltage level on the V line with respect to the R line is
changed to a value greater than six volts, the pre-start alarm controller will issue a CALL EXCHANGE tone
(194Hz) for about 4 seconds. This CALL EXCHANGE tone is transmitted to all intercoms and the surface
exchange pair. This tone triggers a tone detector in the surface exchange that in turn rings an alarm to
attract the exchange operator’s attention.
3. INSTALLATION AND CONNECTIONS
Cable Shielding
From “PRE-START ALARM AND COMMUNICATIONS SYSTEM TYPE PSACS1” user manual (20-079-12)
the following system cables are used: G2000 and G2000B both have a foil and drain wire and cable CABL25
has no shielding at all. The cable is a very important part in the system as it carries all the signals and
distributes power to all the system components. Of the conductors, two are larger in cross sectional area
than the other two. The two larger cross sectional area conductors are used to distribute power to the system
components while the smaller conductors are used to convey signals between the various system
components. The smaller conductors are the ones that have a foil sheath in the G2000 and G2000B cables.
The connection of foil sheath and drain wire is critical for correct installation. You must either use the shield
cable correctly with the ABMA3-1 R-Line (Common line) terminated with a shield drain wire at each ABMA3-
1 or not use a shield foil/drain wire at all, which is the Austdac default method. The shield is not passed
through and is left floating as depicted in the electrically simplified figure 1 over:
