Voice traffic on cellular networks currently is routed with what is known as a circuit-switched system.
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In time, packet networks will almost entirely replace more expensive and less capable circuit-switched networks.
At the carrier switching office, the voice is separated from the data and converted back to regular circuit-switched voice.
They assume a future in which all regulatory differences between IP-based and traditional circuit-switched phone services have been eliminated.
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Circuit-switched telephone systems have been replaced by packet-switched networks (most notably the Internet).
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The question is: What do you do with the billions of dollars worth of obsolescing circuit-switched equipment in the ground?
Much of the problem is that older circuit-switched networks were designed for one purpose: to connect two callers by opening up a dedicated line between them.
Expecting the move, Sprint quit buying circuit-switched equipment in 1996.
However, VOIP differs from the usual phone services in that it sends calls as digital packets of information over data networks rather than relying on a dedicated circuit-switched network.
Pearse and others dream of unifying the mess, with a box that blends both optics and electronics, fusing the circuit-switched world of phone calls and packet-switched world of Internet data.
What's more, Capellas has ratcheted up pressure on rivals this year by migrating 10% of MCI's phone calls from old circuit-switched networks--subject to those antiquated access fees--to the Internet, which is free of them.
Their conclusion is that the switching and transmission costs for IP-based telephone networks are much lower than for switched circuit telephone networks.
CNN: IP telephony is the "in" thing these days, but should it be?
They then analyze how the remaining major cost components, switching and transmission for both types of networks and interconnecting with the switched circuit network for the IP-based networks, change with the change in technology.
CNN: IP telephony is the "in" thing these days, but should it be?
So much so that the extra cost of the gateways that will be needed between the two telecommunications worlds do not bring the costs up to the same level as the costs for switched circuit telephone networks.
CNN: IP telephony is the "in" thing these days, but should it be?
Technologies that let an IP-based telecommunications provider offer IP telephony services commensurate in quality to the traditional switched circuit providers, or at least as good a quality as cell phone providers can offer, are now getting close to being finalized by the Internet Engineering Task Force.
CNN: IP telephony is the "in" thing these days, but should it be?
The spring is wound for half a minute, and then unwinds over six minutes, charging a battery in the process, and providing enough energy to run the radio for an hour. (This means the radio's spring-controller circuit is no longer necessary.) Thus, Freeplay has switched from making solely spring-powered devices to making battery-powered devices that are equipped with a clockwork mechanism for recharging and emergency use.
The Global Positioning System circuit, several power converters and a set of devices that route commands to various pieces of equipment were switched off.
Circuit boards are double-insulated to protect against power surges, and there are backup power supplies that can be switched out on the fly.
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