Posts Tagged ‘computer’

I’d like to use a VoIP service, but would prefer not to have to leave the computer on all day.
Is there any way I can avoid using a PC to make and receive calls – are there any adaptors that can be plugged straight into an ethernet router?

Thanks in advance.

I bought a garmin 200 gps and im trying to update the maps online. The problem is when i plug the usb cable into the computer, my computer does not recognize the device.. It doesnt do anything, usually an icon will pop up saying new hardware detected.. but not this time. Any help would be greately appreciated

I want to download games and other extras onto my Garmin GPS system but sadly i don’t know how

The Global Positioning System (GPS) consists of a number of orbiting satellites that provide precise positioning information for navigation purposes. Positioning is calculated by using accurate timing information and triangulation. However, the accurate timing system can also be used for computer network time synchronisation purposes. Each orbiting satellite has an onboard atomic clock that can provide highly precise time. This article describes how precise GPS timing information can be utilised to provide network timing via GPS NTP servers. It also discusses the type of equipment required to process GPS signals for time and frequency applications.

Time is referenced to Universal Coordinated Time (UTC), which is the same worldwide and does not vary with time zones. The GPS satellites continuously transmit precise time information. GPS time is not affected by leap seconds and is currently 14 seconds ahead of UTC time. GPS time can easily be adjusted to provide UTC time for computer network time synchronisation. The GPS satellites broadcast a very weak low-power radio signal. The signal has two frequencies, L1 and L2. L1 is intended as a civilian GPS band broadcast at 1575.42 MHz. L2 should provide stronger signal transmissions in the future. The signal travels in a straight line and can pass through clouds, glass and plastics but is blocked by objects such as metal and brickwork. Therefore, ideally, a GPS antenna requires a good view of the sky. The ideal location for a GPS antenna is on rooftop with a good view of the sky. If it is impractical to locate a roof-mounted antenna, installation on the side of a building can be adequate.

The GPS system provides a subscription-free accurate timing resource. Many computer networks utilise the GPS clock as an accurate timing reference for computer synchronisation. Precise GPS NTP server systems utilise GPS reference clocks as an external synchronisation source. The GPS system can supply highly precise time and frequency information accurate to a couple of nanoseconds. This accuracy is generally more than enough for most computer network timing applications.

Most GPS receivers transmit time and positioning information in a serial format using the standard NMEA protocol. Information is transmitted as sentences of character strings. Additionally, a highly accurate timing pulse is generated which marks the beginning of each second. This timing pulse can be converted to a RS232 signal level and fed into a RS232 control line interrupt to provide a precise timing reference. When the timing pulse is combined with the NMEA output sentences, a very accurate timing reference becomes available for use by NTP servers or computer timing equipment.

The GPS system is global navigation system introduced by the US military. The system provide navigation and positioning information anywhere on the face of the Earth. The GPS system also provides a highly accurate and precise time and frequency signal ideal for computer timing applications. The GPS system is a orbiting constellation of 24 satellites, each broadcasting time and position information around the globe.

This article describes how the GPS system can be used to provide an accurate time and frequency reference for NTP servers and computer network time synchronisation.

GPS timing information is continuously broadcast by each GPS satellite. GPS time is not affected by leap seconds. Therefore, GPS time is currently about 14 seconds ahead of UTC time. However, offset information is available to readily convert GPS time to UTC time, which is used in NTP server and computer time server systems.

Each GPS satellite transmits information as very low-power radio frequency transmission. Two frequencies are used, one for civilian use coded L1, and one for military use coded L2. The civilian L1 frequency is the most widely used and is transmitted at 1575 MHz. The broadcast GPS signal can easily penetrate less dense material such as plastic, but cannot penetrate higher density materials such as brick.

An antenna is utilised to boost the GPS signal and pass the signal along a coax cable. Ideally, a GPS antenna needs to have as good a view of the sky as possible to receive from as many satellites as possible. Ideally, it should be located outdoors on a rooftop with a good 360-degree un-obscured view of the sky.

GPS antenna systems transmit signals down a coax cable and are sensitive to coax quality and cable length. The coax type and antenna gain determines the cable length that can be utilised by a GPS antenna. Higher quality coax cable generally have much lower attenuation figures and hence provide much longer cable runs between the receiver and antenna. Typically, a low-quality coax can run to 20-30m, while a high quality coax can be used in excess of 100m cable runs. To increase these distances still further, a GPS amplifier can be used to amplify and boost the received GPS signal.

GPS timing systems also utilise a GPS receiver in order to decode the received GPS transmission and convert it to a computer readable format. The GPS receiver processes the transmitted GPS positioning information and provides a readable serial transmission as output. GPS NTP servers and computer time servers may also utilise a precise pulse per second output generated by the GPS receiver to provide ultra-precise timing. The pulse per second timing pulse on most receivers is accurate to within a few milliseconds of UTC.

To summarise, the GPS system is ideal for synchronising NTP server and computer time servers. Accuracies of a few hundred nanoseconds can be reasonably achieved with low-cost GPS receiving equipment.

I am doing a project for school and I have the basic fundamentals down for implementing the system. I was wondering if it was possible with a functional VoIP Phone at an office for a user to connect to his/her phone from their home?