DuraFon Best Practices
The DuraFon has different modes of operating. Below is a visual representation of the operational modes:
TWO WAY/INTERCOM MODE
The handset in this mode will be full duplex; (the handset can talk/listen at the same time), in which one DuraFon handset (HS) may communicate with another DuraFon handset (HS). Both handsets must be registered to the same base station (BU); or base station group in multiple BU deployments.
In this mode the HS will be connected to the BU and have a full duplex communications with the BU. The range will be the greatest distance as the HS is going through the BU.
In this mode the HS to HS communication will be half-duplex (the handset can talk or listen only, not talk/listen at the same time). A special broadcast option is available only with the PRO model (base assist broadcast) and it allows a desk phone going through a PBX to ring all HS assigned to the base/ base group in a simplex fashion (Only downstream broadcast communications from BU to handsets).
The DuraFon system has a default group 00 that all HS’s registered to the BU will be a part of, and it
cannot be removed. So when an HS is in one group it is really in two groups, the default group 00 and
any group from 01-07. This is done to ensure that all HS registered to the BU will be included in a
broadcast transmission, either initiated by a HS or the BU.
HS to HS and HS to BU Range Difference
Below is a graphical illustration of the range you would expect in different modes of operations. As you
can see since in 2-way/Intercom mode the HS is communicating to another HS with its own radio and
not going through the base, the range of this type of communication will be up to 75% less range for all
DuraFon HS’s with the exception of the DuraFon UHF HS.
The next step is to determine if the signal, from the handset’s perspective, is within range to maintain
quality of service operations.
RSSI Tool and How to test for range on the HS
Please do not have any other BU or HS in use while running the test.
RSSI stands for received signal strength indicator. In the dBm sale a higher negative number is a weaker signal then a lower negative number, for example -80 dBm is weaker than -43 dBm. Please use -80 dBm as your guide for determining maximum coverage of the DuraFon system in multiple base deployments or in environments where RF interference exists in the 902-928 MHz range. For single base deployments the RSSI could be as low as -90dBm in clean RF environments.
-80dBm or better
-81dBm to -90dBm = low risk of dropped calls but a slight reduction in voice quality.
Signal -91dBm to -100dBm = real risk of random dropped calls and noticeable voice quality reduction.
Signal <-101dBm = terrible voice quality and dropped calls.
Signal <-110dBm = no link at all.
In order to access the RSSI tool in the handset please follow the following steps. First press the softkey under menu. Then press *,#,#,*.
After you go through the above steps you will see the following screen. Please select base number of BU you want to test RSSI to.
DuraFon 1x BU values are 10-40. Pro BU values are 00-07.
Press the number 1 on the keypad to access the BER menu.
When you see this screen with H16K and B16K values then just press the * button to access the screen where it will display the RSSI value in dBm.
Note: If you do lose the link between handset and base, exit the menu, and enter back in it again.
RSSI does not show you raw radio frequency (RF) background noise that may degrade the quality of the RF signal, RSSI only shows the strength of the signal. One signature of RF interference is good RSSI readings, but poor quality performance. If you suspect RF interference please use a spectrum analyzer that can detect RF signals in the 902-928 MHz band.
The FREQ scale measures frequency deviation in Hz. The frequency deviation should not exceed 2000 Hz at a distance of less than 20 ft from the BU. If you experience a frequency deviation of more than 2000 Hz from the BU at a distance of less than 20 ft. from the BU then that would most likely be an indicator of a ďad HS aŶd it ǁould Ŷeed to ďe RMA’ed.
It is important that if any changes are made during the RSSI testing, other than the HS distance to the BU, such as a different antenna on the HS or BU relocation, that the changes be made one parameter at a time, and after each parameter change the RSSI test is run again to see the difference that one change at a time causes.
Note: Using the short antenna on the HS may cause up to a -5 to -8dB difference compared to the long antenna in real world deployments.
Generally, the handset-to-handset range is only about 25% - 50% of the handset-to-base range. There are three ways to improve DuraFon handset-to-handset range, in order of increasing cost:
- Use of the larger antenna on the The long antenna clears the side of the head, leading to an effective five to seven dB gain on each side. This long antenna makes the antenna on the HS now more susceptible to breakage due to the amount of protrusion the long antenna has compared to the short antenna.
- DuraFon Pro repeater A DuraFon Pro repeater BU can make the range match that of the handset to base, but these can be tricky to set up, maintain, and add to the probability of self interference in your DuraFon Pro system . This solution is now being deprecated in favor of option 3.
- DuraFon UHF: The UHF radio has a longer wavelength and a higher transmit power, both of which contribute to increasing the The handset-to-handset range at UHF (450 – 470 MHz) comes out to be approximately the same as the handset-to-base range at 900 MHz. This is the preferred solution we are recommending going forward (i.e. preferred over the repeater option), but it naturally requires the use of DuraFon UHF handsets and DuraFon Pro BUs.
Single Line BU Spacing Considerations
In order to avoid self interference with other BU’s in a multiple single line BU deployment please space
the BU’s at least 30 feet apart from each other vertically as well as horizontally.
If using external antennas with the BU’s then spacing requirements of the external antennas is now 30
feet in all directions, and there is no longer a spacing requirement for the single line BU’s.
The DuraFon SIP BU looks just like a DuraFon 1X BU, but it has an RJ-45 jack as well as a GUI to manage the BU via a web browser.
The DurFon SIP has an RJ-45 Jack for making/taking SIP calls and an RJ-11 jack for taking/making regular
POTS calls. The DurFon SIP BU supports up to four concurrent calls. The RJ-11 jack only supports one
number/extension so the possibilities of the concurrent calls are 4 concurrent SIP calls total, with no
POTS call, or three concurrent SIP calls with one concurrent POTS call. Below is a diagram of four
concurrent SIP calls to four DuraFon SIP HS’s.
It’s important to note that the DuraFon SIP HS’s only work with a 900MHz link to the DuraFon SIP BU.
The DuraFon SIP HS cannot by its self be registered to a SIP server without the DuraFon BU. TAP is also
not supported with DuraFon SIP. Also other HS’s, not already in established communication with the
BU, can be communicating to each other in the 2-way/Intercom mode, so long as the HS you wish to communicate with is not communicating with the BU or occupied by other 2-way/Intercom communication with other HS.
Here is an example of three concurrent SIP calls with one analog call. The analog line can be used as a backup if connectivity is lost to the SIP server. The analog line can also be connected to a door call system, an analog PA paging system, a call box, an entry controller and many more applications.
The maximum number of DuraFon SIP HS’s that can be registered to a DuraFon SIP BU is ten. Only one
DuraFon SIP HS at a time can be registered to only one DuraFon SIP BU at a time. One DuraFon SIP BU
can support a maximum of ten SIP accounts, but can only support four concurrent SIP calls at once, so
only four DuraFon SIP HS’s at any time can communicate to the DuraFon SIP BU while having either an
analog or SIP concurrent call. The DuraFon SIP is a single BU setup; you cannot have multiple BU’s
sharing the same group key like in the DuraFon Pro or DuraFon-1X systems. You can deploy multiple
DuraFon SIP BU’s at a location, but they have to be treated as standalone systems and have proper
spacing of the BU’s, or if using external antennas, proper spacing of the external antennas.
Unfortunately at this time the DuraFon SIP does not support TAP.
Below is a simplified diagram of a Nurse Call TAP deployment.
Our phone systems also use the 900 MHz frequency as well, so before deploying our phone systems in
an environment where nurse call systems are already in place, or planning on being deployed, it is highly
recommend that a 900 MHz wireless sight survey is preformed using a 900 MHz spectrum analyzer to
determine if the location can accommodate both systems running without causing a noticeable detriment on either systems operation. Newer DuraFon TAP BU’s have a USB type B female jack located in the back of the BU for upgrading the firmware of the BU in the field and also to run the TAP service if TAP service is desired. If TAP is desired please be aware that out of the box, the DuraFon system will not support TAP. If TAP is desired please inform your sales representative that TAP will be needed to be preloaded on the DuraFon system so TAP will be supported out of the box on the system that is purchased. If TAP is required after a phone system has been deployed, then please contact one of our support representatives so the HS can be shipped to us for a firmware upgrade to support TAP, and if your BU has a DB-9 serial connector the BU will also need to be shipped back to us so we can perform a firmware upgrade on the BU as well. If your Nurse Call server has only a serial DB-9 connector and your DuraFon TAP BU as the USB type B connector, you can install a serial to USB dongle on the nurse call server and install the appropriate drivers on the server to get the nurse call server communicating with the DuraFon BU that supports TAP. TAP will use group 00 so all HS’s with TAP firmware will get the TAP message.
The DuraFon UHF HS has a dual radio in the HS. It is capable of communicating to the DuraFon Pro BU
on 900 MHz or communicating with other UHF radios at 461-469MHz. Please note that this is not dual
band concurrent, it is dual band switchable, so you can only communicate with either the DuraFon Pro
BU or another UHF radio, not both at the same time. Below is a list of pre-defined channels and their
respected mapped frequencies. The DuraFon UHF HS’s can support frequencies from 450-470MHz, if
you need channels mapped to other supported frequencies then Contact EnGenius to request this
and have all desired frequencies and offset (repeater splits TX and RX) known ahead of time.
The DuraFon UHF can also be used with other UHF vendors as well, so long as the DuraFon UHF can match the other vendor’s UHF system or HS’s frequency as well as CTC/DCS. Below is an example of our DuraFon UHF HS communicating with a Motorola CLS1410 UHF HS.
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Very interesting article!
In the dBm sale a higher negative number is a fireboy and watergirl weaker signal then a lower negative number, for example -80 dBm is weaker than -43 dBm.
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