do they want to have a back up to their main dispatch, as in a way to page out as a back up to a conventional system? If so, warning systems ( http://www.warningsystems.com/products.htm) has some products that allow you to do text to speech conversion and page out from a web application from anywhere, but as others have said, this would not be good for your primary system, and should be only a backup or redundant part of your paging system. The voip over the internet is still unstable at best, and QOS is sadly lacking in a lot of telephone companies and internet company's, if you have a remote need to dispatch, lease your own line, use good quality equipment, and have the internet or phone company administering on speed dial, as a remote link it may be your only choice in some situations, but with conventional wired telco's loosing customers in droves to wireless, and infrastructure aging, it's as someone else said the best solution is a microwave link.
On Tue, Nov 24, 2009 at 5:36 PM, Chris Quirk <[email protected]> wrote: > > > Not sure why people think voice over IP is cheap, it is less costly but > cheap ? 100% monitoring of line quality, multiple T 1s with different > carriers and still support a micro wave link to back all this up. When the > T1 (s)goes down and Micro is up we lose significant capacity on the system > however it is meant to be a partial not a full back up. > > If you are in an area where one carrier and only one carrier is brining it > into you building you have a single point of entry with no back up if some > tech cuts the copper in your area you are in real trouble as they may not > know who did it for hours. > > We lost all communications in the San Jose area earlier this year as a > result of a cable being cut by an angry employee. no 911 service either. > > > > --- On *Tue, 11/24/09, Nate Duehr <[email protected]>* wrote: > > > From: Nate Duehr <[email protected]> > Subject: Re: [Repeater-Builder] setting up a repeater for dispatch > > To: [email protected] > Date: Tuesday, November 24, 2009, 1:43 PM > > > > > Time for my favorite rant -- pardon me for a moment: > > The more important point for putting Public Safety on IP networks (of any > sort) is that the IP link has MONITORING built in. > > Most (even so-called "Public Safety ready") IP linking systems DO NOT have > ANY way to notify the dispatcher that their transmissions are NOT going out > over the air, or that the link coming in from the field radio units is down. > > VoIP/RoIP is "cheap" but you get what you pay for. Engineering it properly > and MONITORING the links is essential, since lives are on the line. > > I helped some folks test the very early EF Johnson Ethernet ports on the > back of their repeaters, and custom "dispatch" software that tied a headset > on the sound card on a PC to the repeater(s). The system used Multicast IP > (mistake number one), UDP (maybe mistake number two), and when I said, > "Unplug the Ethernet jack from the repeater" while the dispatch console was > "transmitting"... there was ZERO alarm indication ANYWHERE to tell either > the dispatcher, the officers in the field, or the technicians -- THAT THE > SYSTEM WAS DOWN. > > This problem is by no means limited to EFJ, it's just the one I saw in > person on a test bench with my own two eyes. RoIP engineers need to pull > their heads out of their you-know-what's, and start THINKING again. RF > links had a continuous tone on them in most systems for a REASON -- the link > was DESIGNED to be continuously monitored by a dry-alarm contact at both > ends. > > Whether or not the system engineer actually took the time/money/effort to > USE those dry-contacts and alarms in their system plan, is a whole different > story. But most RoIP implementations DON'T EVEN HAVE THEM. > > Avoid any that don't. Engineering done properly will pay off later. Just > because government agencies can't be sued for liability (who's bright idea > was THAT?), doesn't mean the system engineer should do anything less than > the best job possible for the officers in the field attempting to contact > someone for help. > > RoIP/VoIP is "gee whiz" technology when it provides a link that would > otherwise be cost-prohibitive or impossible due to terrain. It's "oh shit!" > technology when it fails and no one in the dispatch center knows it's down. > "Hero to zero" in one second flat. > > BUILD NETWORK MONITORING INTO YOUR VOIP/ROIP APPLICATIONS PLEASE. > > Done with my rant... if it doesn't apply to the technology you've chosen, > ignore. If there are those reading along who just had an "oh shit!" moment > thinking about their VoIP/RoIP network that's already deployed... go write > up that budget request for monitoring and FIX IT... now. Before your > bouncing IP link someday kills someone. > > -- > Nate Duehr, WY0X > [email protected] > > > > > > > > -- Major John Gleaton Escambia County Sheriff's Office [email protected] 251-241-9203 "I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." --Thomas Jefferson
