VoIP, Serial over IP, et al

Rob Brookes' Blog - MRMap and Communications Info

VoIP, Serial over IP, et al

Postby Rob_Brookes » Tue Nov 01, 2011 12:23 pm

The recent coming together of a number of North West MRTs who were independently looking into aspects of remote control of hardware via the internet and the transmission of voice messages via the same media (VoIP), has engendered considerable interest from other teams around the area. Originally this post was to feature work being done by Tom at Holme Valley MRT in setting up a Sigs vehicle, (C3 or Forward control vehicle depending on your upbringing). It includes innovative use of MRMap and as this is after all, why we are all here, I take the opportunity to feature such work whenever I can. This post is assembled from Tom’s notes to me.

Holme Valley Mountain Rescue Team use Simoco SRP 9180's fitted with second generation GPS speaker mics and they also have a few mobile phones working into MRMap.

The control vehicle is setup with an SRM9030 dual control head providing a feed into a laptop which in turn has a 32inch LED screen plugged into it. Also in use is a Vodafone monthly contract dongle with enhanced coverage provided by an external aerial on the vehicle roof. This is plugged into a dedicated socket on the dongle using a lead from Panorama.

Two copies of MRMAP are running on the computer. The first is setup to connect to the SRM9030 radio and to the MRMAP servers via the dongle. This is used to provide an overview normally using the 1:25k maps for the controller to get the bigger picture. A second copy of MRMap runs on the laptop screen connects only to the servers so that they can work on incidents looking at different map scales and areas etc, whilst still getting the location of team radios from the servers via the dongle.

Holme Valley MRT base is setup the same with Radio, Internet and two screens, they have been experimenting running control from HQ getting the data via the servers from the vehicle dongle but for a voice link they have been using two airwave terminals meaning the van acts as a link/forward control but that the HQ to vehicle communications is handled via Airwave so distance is no problem. However, it still means someone has to relay the voice messages hence the interest in the VoIP project being carried out jointly by a number of North West MRTs, with each team dealing with a specific element of the task but until recently, unaware of the work of others.
Holme Valley also have a mobile Rebroadcast built using SRM9000 radios inside a Peli case
and they’ve also built an all in one mobile set for use anywhere, sometimes needing to control incidents from police stations etc. It has a dedicated laptop inside and 12v and 240v power supplies so can run anywhere including middle of a field off a battery if needed.
image (4).jpeg

Currently they are looking into text messaging sent over the radios from the computer for sending out group info IE, cas finds and grid references etc. The aim is to achieve something similar to the data/dispatch system now found in county ambulances all over the country. To this end, I’ve given Tom some software written by myself that allows computer keyboard entered text messages to be sent over the air to and from a Simoco radio. This is test and diagnostic software and not up to the standard of Dave Binks by any means! If enough people prove to be interested in text messaging then maybe we’ll have to pile yet more work onto Mr Binks.

More information on serial control over internet and VoIP will be posted as I get it but if any team is interested in the work being done by teams up here, please let me know and I’ll pass on the contact details. If you’re already doing work along these lines then please let us know and maybe together, we can help shorten the development time. We currently have teams running trials of serial control of Simoco radios via the internet. That includes getting GPS data only, back from a remote monitoring site but also includes remote re-programming of the same radios without having to actually visit the site. Using software that’s not at all difficult to write, it could also be used to provide remote channel changing of the radios at the site in the same manner police/ambulance dispatchers already do. Control of these radios is via a serial interface using a proprietary protocol. Thanks to a lot of help from Simoco and TMC in Australia, we know how this protocol works and basically, anything that can be done via a 9030 control head can also be done via computer software located in your base.

Another team is looking at using device that provides two-way voice messaging via the internet and out to a remotely located transmitter site. The advantage in both these cases being that a conventional telephone line is very much cheaper than a dedicated data line used to provide landline control of remote sites. Even when the necessary broadband is included, it still works out much cheaper than leased lines. In cases where a direct radio link isn’t possible, the internet is a viable option. The current aim is to combine the operation of both systems described above so that total control of all elements of a remote radio site becomes possible from the comfort of your own team base.

All the devices being considered are commercial, off-the-shelf units and at the moment, none of them look like rocket science to get up and running. Certainly a wealth of experience is available to anyone wanting to become involved in projects such as these and there’s not really a better way to learn how to do something than to give it a try or ask someone who already has! All the teams involved are prepared to share their experiences.

The initial work on remote serial control of radios uses a device called NetCom Mini from Roalan on

The VoIP work is currently looking at a device called a Trip made by AW Communications in Carlisle on

Work by all teams involved is currently in the process of being collated.
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Re: VoIP, Serial over IP, et al

Postby Rob_Brookes » Tue Nov 15, 2011 11:47 am

A little more on this one.

Hopefully at the next LDSAMRA comms sub committee meeting on Nov 29th we will have Adrian Charlton of AW Communications coming to talk to us about his companys products, in particular the VoIP Trip boxes and the new touch screen desktop controller.

We now have sufficiently stable broadband in the Lakes so that using the internet instead of a long wire, leased landline becomes a viable option. Admittedly, the internet can go down and take your comms with it but during my time as Kendal's radio officer, I wouldn't like to count the number of times the BT leased line up to our remote site, or the main telephone exchange, went down because it had been hit by lightning. Meeting a BT engineer on some lonely country road at 1 in the morning is not my way of enjoying myself.

Modern broadband speed and the hardware associated with Voice over Internet is a lot better than it was and both voice and GPS data can now be independently passed back to your base regardless of distance or intervening hills etc. All you need is a remote site positioned to give you optimum coverage of the area you want to improve comms in and a broadband telephone line up to it. BT leased lines are ridiculously expensive so the annual cost of a broadband line is virtually nothing in comparison.

The line needs a fixed IP address but doesn't necessarily need to be of industrial ruggedness. A 'domestic' broadband line will also work but will possibly be subject to more failures although these days, that will be as many as you currently get at home.

You really need a low contention Internet Provider if you can find one. Most domestic providers throttle back the line speeds anything up to 50% when the children come home from school. If you can find one that doesn't and quite often these days their adverts will announce that they don't (but not if they do!!) then go for this one. The bandwidth requirement of modern VoIP hardware isn't too high so you might get away with it using any ISP. This is one of the many questions for Adrian.

At your base you need a desktop controller, there are others of course but we're currently only dealing with AW Communications and so generally refer to their kit. This controller resembles a normal telephone but has a keypad or touch screen depending on the model and the newer versions have the VoIP electronics built in. Both transmit and receive audio, the latter at loudspeaker level, is handled by the controller which plugs into one of the ports on your base broadband router. No radio is necessary at the base for this system.

At the far end of things which can be virtually anywhere in your area, you have a broadband phone line with a fixed IP address, another router and your VoIP box. From AW Comms it's called a Trip but there will be others you can use. This box connects to your radio which can be as sophisticated as a full commercial repeater or as simple as a single vehicle radio. The Lakes use Simoco radio hardware because it performs better than the others so in our case we could connect anything from a TSF2025 base station to a simple SRM9000 vehicle radio. Plug in the aerial and that's it.

At your base, operate the PTT on the controller microphone and your transmission is heard wherever your remote site is located. This system has it's faults. Broadband can go down. Overhead telephone wires can break. Nothing is perfect but for those teams who can't afford a BT leased line or who can't get a direct radio link up to their remote site. This will provide you with comms into those difficult areas where you need coverage.

At this moment in time it would be silly of me to be recommending that any team switches to an internet-based primary communications system. I would still say that a direct radio to radio method should also be available for that 'major incident' that never seems to happen and then bites you in the bum when it does. However, internet-based communications does have a part to play and has moved on from being a kid's toy. Anyone who has had Skype phone calls lasting hours will know how reliable the system can be. The methods we are describing here are based on the same technology and are equally reliable. Nothing is perfect even a straight radio can fail in the field but I personally believe this method is worthy of consideration and has a part to play even if it entails speaking to your local farmer whose house overlooks your bad comms area and offering to pay his broadband charges if he lets you install some kit. There are always ways.

The systems and the hardware are not cheap. Very (!) rough guestimates of pricing put it somewhere around the annual cost of a leased phone line. However there are no more costs apart from that of the broadband line. Once you've paid for the hardware, it's yours.

The notes from this meeting when sorted out will be posted here for any interested teams. We will be able to answer a limited number of questions but any team outside our region who is interested in this topic should contact Adrian via his website. He's very approachable and knows his products inside out. He also knows how mountain rescue operates and has done a lot of work with Lake District teams and even that didn't put him off.
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Re: VoIP, Serial over IP, et al

Postby Rob_Brookes » Sun Dec 04, 2011 3:44 pm

As usual I have to add that I have no commercial affiliation with any of the companies mentioned in this and other posts I've written. We recommend a manufacturer usually because their kit has been tested by us and found to do the job it's advertised for. Life's too short for me to carry on looking after that. If anyone wants to add any other providers of same or similar hardware then by all means do so but I won't be able to provide anything further to what you add yourselves. - Rob

The page covering the NetCom Mini Ethernet to serial server has been updated after an error I made was pointed out. The NetCom Mini device is only needed at the remote end of the system. The base end is handled by NetCom software that sets up a virtual com port. Sorry about that.

Attached is what I hope is a graphical interpretation of Adrian Charlton of AW Communications, presentation to LDSAMRA on Voice over internet where it applies to us and our communications systems. Also included is the GPS-data only system designed by Jon Beavan and Tom Redfern at Cave Rescue Organisation. This is a very much simpler and cheaper system than the full VoIP one described by Adrian but if you don’t need the voice signals to be included or you handle these another way, Airwave for example, then this method may be all you need. The principle is not Simoco-specific if you don’t use Dave’s MRMap tracking application. It’s purely a transparent method of sending any type of serial data over the internet. Icom and Motorola data formats could presumably be handled in the same way for example.

As well as receiving GPS data, because the computer is not aware of the internet link in this and sees only a comport attached to your computer, you can also communicate in any way you wish with the remote radios. Programming can be updated remotely and MRMap has no problem polling team radios via this system. As MRMap can be connected to up to 99 radios I think it was at the last count, you can handle the input from as many radios as you have serial ports on your machine, you’re never going to be fitting 99 I would suspect. There’s no reason to suppose the NetCom Mini server cares at all if you connect it to your computer via a USB to Serial adaptor rather than to a proper RS232 port.

AW Communications TRip device adds another layer of functionality by way of also handling voice signals. You don’t need a computer at your base for this although you do need one if you run MRMap of course. There is no need for any radios to be at your base for this system although I wouldn’t go so far as to say you can remove all your existing radios! A computer is not required at the remote site which is a huge advantage of these systems as running Windows where you can’t see it is just never going to work reliably. These devices run embedded Linux incidentally.

What it will do is give you access to better radio sites in those cases we’ve all experienced where the Parks or whoever won’t allow a decent aerial to be put up at your base. Find somewhere any distance away (and I do mean ‘any’) and fit it with a broadband phone line. Connect up Adrian’s boxes to a remote radio and reap the benefit of having a very efficient aerial ‘on your roof’.

In the case of the TRip device from AW Comms, there are also eight available IO ports on the device. They can be programmed as either input or output so an input at the remote site triggered by mains failure, becomes an output at your base that tells you you’re running on battery power for example. Even your burglar alarm if you have one at your site can be fed over the internet back to your base. Likewise it can be reset from the base over the same IO ports. One of the very useful but hopefully never used, functions for this is as a transmitter ‘kill switch’ in the event that the transmitter locks up for whatever reason. It can be reset from the base without any need to visit the site. Another use would be in providing a remotely operated ‘Hot swap’ function where a back-up repeater was switched in from the base should the main one fail. These fall under the ‘as many uses as your imagination runs to’ category.

One final thing the TRip device can do is contained in the fact that it has two internal IP addresses, the primary one and a backup. Should your main base system become unavailable for whatever reason, the secondary IP address can be activated from elsewhere and so control of your remote transmitter sites can be handed over to another location. This could involve you having both a fixed base location and an internet-equipped vehicle. Both of these would be able to control all your remote sites by using the two IP addresses. In the case of the vehicle, this could be from anywhere in the country of course. Although there is a transmission lag when using the internet, you will seldom be able to hear the output from the base whilst you’re actually operating it and so will never notice. Anyone who has tried to talk to someone on an Airwave terminal whilst standing within earshot of them will know what I mean.

Like anything to do with the internet, these systems are only as good as the web connection you provide it with and when that goes down, it takes your comms with it. In CRO’s case where they are just handling GPS, this isn’t going to be critical in any way and they could undoubtedly live with it. However once you begin passing your team voice comms over systems like these then it does become more critical and personally I’d have to suggest that these methods are used in parallel to conventional comms systems that use radios at both ends even if this means fitting out repeaters or rebroadcast in your vehicles so you can revert back to the ‘old’ methods should the internet fall over, and it will at some stage. However, as has been said before, for the number of times I was called out in the middle of the night to get Kendal’s leased line put back together again, I’d have to say that the internet can’t be any worse!

I’d be misleading you if I said these systems are ‘plug-and-play’, they do take some setting up with fixed IP addresses and port forwarding in your router but we now have a wealth of both experience and technical know-how available to us and two teams have got the CRO system working so there are people you can talk to about doing it for your own team. Adrian at AW Communications is a lot more than a salesman (he’s MD and ex Pye/Philips in fact) and he can give you an answer to pretty much anything you are going to ask when it comes to his company’s products, we got an excellent demonstration of that at the last LDSAMRA meeting!

This probably concludes my involvement in this as without the ability to set up hardware myself I’m dependent on others providing me with information I can then pass on to you. I do get a lot of stuff in response to the ‘Can you write it up for me?’ that comes back as ‘It worked’. Not much use usually but in this case I’ve had good feedback from CRO and others but this is still at about the limit of what I can do. The LDSAMRA Comms sub committee meeting produced nearly 10MB of documentation on this and other subjects and some of you will have had the links to download this. Most of it comes from the web sites of the various companies supplying the hardware but some is home-grown.

If anyone needs any further information on this subject then you can by all means contact me but my reply may well be to put you in touch with those who know more about it than I do. If I’ve made any mistakes on the attached diagrams, I’m sure someone will tell me.

Adrian is on http://www.awcsl.co.uk/ and the NetCom Mini Ethernet Server came from http://www.roalan.com/contact.htm Both CRO and Cockermouth teams have practical experience of the NetCom Mini device.
VoIP_GPS rev A.pdf
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