66250756-EN - V2.1 - 05/11/19
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4000 Series GSM Lite Audio Intercom - Technical Manual
4000 Series GSM Lite Audio Intercom
Additional User Information
UNDERSTANDING THE SIGNAL STRENGTH (SIG) AND BIT ERROR RATE (BER)
When a request for signal strength message is sent to the GSM LITE intercom it will reply with a two part code.
The first part of the code is a signal strength code
SIG
which will be between 0 – 31 or 99. Ideally the signal strength should be as
close to 31 as possible for the best possible performance. The lower the number, the weaker the signal. Signal strengths lower than
10 may cause operational problems such as loss of speech quality (and possibly missing DTMF tones) and/or network loss. A signal
strength of 99 indicates it could not be detected.
The second part of the code is the bit error rate
BER
. The bit error rate is used in digital telecommunication as a figure of merit for
how effectively the receiver (in this case the GSM LITE intercom) is able to decode transmitted data (the data in this instance are the
various text message commands used to program the GSM LITE intercom, described on pages 29 - 40, speech and DTMF signals
used by the GSM LITE intercom for normal operation). It is the percentage of bits that have errors relative to the total number of bits
received in a transmission. Ideally the
BER
code should be as close to 0 as possible, the lower the
BER
the better. High
BER
codes can
be caused by noise, interference, distortion or bit synchronisation errors over the transmission of data to the GSM LITE intercom and
as a result the problems described above (loss of speech quality, possibly missing DTMF tones and/or network loss etc.) can occur.
The example below shows the ideal reply to expect when the signal strength query
1111SIG?
is sent to the GSM LITE intercom:
SIGNAL
=
31
BER
=
0
OK
VIDEX
GSM
To achieve the best overall performance from the GSM LITE intercom a high signal strength
SIG
and low bit error rate
BER
is required.
In the event that a low signal strength and high bit error rate is recieved it is recommended that the
Art.432
antenna is repositioned,
where permissible, at the highest point to achieve the best signal. Where this is not possible an alternative high gain antenna can be
used, in particular Videx recommends using the
ANT-GSM-2dB-5M
or
ANT-GSM-2dB-15M
high gain antennas or another suitable
GSM antenna with a standard SMA male connector.
DIALLING INTO THE GSM INTERCOM FROM ANOTHER TELEPHONE
There are three possible outcomes to dialling into the GSM LITE intercom depending on the telephone number you are dialling
in from and the features setup during programming. The three possible outcomes are shown in the table below and are shown
in order of priority. For example, if the number is programmed to automatically activate the relay, this will take priority over the
following two options and if the telephone number is stored as a telephone number called from one of the push buttons, this will
take priority over the last option.
FUNCTION
REQUIREMENT
PRIORITY
Dial in to open the Door.
After dialling the GSM number, the relay will activate
and the call will be dropped.
The telephone number of the telephone dialling in
must be stored in memory location
(
dial to open
list) STR000 - STR099.
1st
Dial in to activate a call (live speech, activate relay/
auxiliary AO1).
After dialling the GSM number, the call will be
answered and two beeps will be heard. The speech
will then be live.
The telephone number of the telephone dialling in
must be stored in memory location:
STN001 - STN004
STD001 - STD004
2nd
Dial in to open the speech from a telephone number
not stored in the GSM intercom.
After dialling the GSM number, the call will be
answered and two beeps will be heard. You will then
be required to enter the 4 digit code to open the
speech.
If neither of the two requirements above are met.
3rd
UNDERSTANDING THE BEEPS
Functions and errors are indicated by beeps from the GSM LITE intercom panel. The following table will help you understand the
different beeps heard and what, if anything, needs to be done in response to the beeps.
BEEP
REASON
SOLUTION
Short beeps at 1 second
intervals.
Relay or auxiliary output activated.
None, this is normal.
Single short beep while
the system is in standby
and not being used.
A valid text message has been received and
processed.
None, this is normal.
