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MDS-VDS Call Priority Analysis

16 décembre 2013

A deep analysis & test has been performed over the behavior of the MDS-VDS system in terms of call priority/behavior, trying to take into account a wide range of situations and factors.

Among all FERMAX available systems, talking about projects with a lot of potential and functions, perhaps one of the most famous systems is the MDS-VDS combination.

MDS-VDS allows to face really big projects with lots of door-panels, Guard Units, General Entrances and Interior Blocks.

Just due to the high number of devices which can be present in this kind of systems, also the communication can be established from a wide different number of locations and modules.


Different variables come into play when looking at the different possibilities:

- Location: one call can be made from different places along the system, like MDS Guard Units, MDS Door Panels, VDS Door panels, VDS residence terminal... 



-Priority: after one call is launched, the rest of users can still try to make a call during the lapse of time when the previous call is already in progress. So there should be some specific rules which automatically either allow or deny the user about sending the call.



-Time parameters:  we also find the parameters “Minimum” and “Maximum” conversation time. These parameters impose certain limits in the system, which are affecting the behavior regarding the priority of the calls.


Thus, if we start thinking thoroughly about how the system will behave when the user makes a call for each situation, and then we wonder if either the system will display “SYSTEM BUSY” or not, or even how long we will have to wait to get the channel free again...then we will notice that this is not a trivial matter...and if we go really deep inside, it can be a bit difficult to guess the result.

In order to clarify these mixture of situations as better as possible, a deep analysis & test has been performed over the behavior of the MDS-VDS system in terms of call priority/behavior, trying to take into account a wide range of situations and factors.

The results have been collected and exposed in a spread-sheet EXCEL document which shows all the studied cases by following a structured and orderly manner.

Regarding the document itself, once the file has been open, a general MAIN INDEX page will be displayed:



Then you must choose first a “CASE ID”. The different cases (from A to E) are reflecting which is the first call event that is generated inside the system, this is called the “STEP 1” action in the document.  Afterwards, you will be forwarded to a specific screen, depending on the chosen CASE.

Once you are inside the specific CASE screen, you will see all the different possible situations, called “STEP 2” calls. Then you can choose among the different situations and find find out the result: if the call is either “POSSIBLE” or “NOT POSSIBLE”.

Let’s have a look now to a real example, in order to clarify how this EXCEL document can help us.


“Initially one tenant has made a call from the MDS Door Panel towards one of the residence VDS terminals.

Meanwhile, a second user is trying to call from another MDS Door Panel. As additional information: this second panel is connected to the same Central Unit than the first panel where the call was launched from (i.e. no FXL BUS in the path).”

For us, the “STEP 1” corresponds to “MDS Panel to VDS Terminal” this is “CASE A”.



Now the “CASE A” screen will be shown. Then we must look for the kind of call that the second tenant pretends to send, i.e., we have to choose call type as “STEP 2”: “MDS Panel on same C.U.”



As a result, we got the required information about the behavior of the system for this specific situation by reading the cell content in the “Result” columns of the grid.



For this particular case, when the second user tries to call, then he will get “Channel Busy” message on the panel display and cannot send the call until the “minimum conversation time” is elapsed (called “tmin”) in the EXCEL.

After this “tmin” is over, then the second user will be allowed to call from the MDS Panel.


This EXCEL document is available for downloading at link below:

MDS-VDS call priority analysis


From FERMAX Technical Department, we trust that the information provided by this document will be helpful to those technicians who are dealing with MDS-VDS system, in order to clarify how the system will behave in terms of "call priority".