In the ultra-short wave conventional wireless communication, the hand-held interphone is often faced with a short communication distance. Because the handset is constrained by many factors such as volume, weight, and power consumption, it is impossible to increase the power substantially and use a high-gain antenna to expand the communication range. Usually this problem is solved by using a repeater to increase the communication distance of a handheld wireless walkie-talkie. Since ultra-shortwave belongs to line-of-sight propagation, as long as the repeater is placed high, high-gain antennas are used and the transmit power is appropriately increased, the communication distance between the portable devices can be effectively extended. The repeater station receives information at a certain set frequency, receives the information at another designated frequency, and transmits the received information as it is. The repeater station is often placed on the top floor of the building, on the tower or on the mountain top.
Repeated stations often have blind spots in the radio coverage area, mainly because the obstacles cause a large attenuation of radio waves in a certain range and cannot communicate. For example, in a city, due to the blockage of a building, the signal in the area near the building is greatly attenuated, and the signal near the building (especially in the direction of the propagation of electric waves) is weak. But away from the building, handheld radios can communicate because of enhanced radio wave diffraction and increased radio wave signals. Another example is that in a building, the base station and garage have very weak radio signals and the handset cannot communicate, but the building can still meet the handset communication. The so-called blind area is within the scope of effective communication, and there are some areas that cannot communicate because of various reasons. Handset communication to solve these blind spots can be implemented by adopting a direct player and power distribution method.
Power distribution method
The power distribution method is mainly applicable to the communication of handsets in various floors and basements of buildings, underground shopping malls, underground multi-storey car parks, etc., in particular building security and handheld communication of underground parking security. Power allocation is to distribute the power of a transmitter to several spaces to solve the user communication between the spaces caused by wall and floor blocking. For example: For a 30-storey building, there are two floors underground. Hand-held walkie-talkies to solve the building's security, on different floors and basements, how to talk to the monitoring center and between security guards. To solve the building security handset communication, power distribution method is needed. If the signal power of the distributor is not enough, a small power amplifier can be added, and the signal can be amplified and then transmitted.
Straightener
The repeater is a frequency selective amplifier that directly amplifies the signal. It is a two-way frequency selective amplifier, an upstream amplifier and a downstream amplifier. The upstream amplifier amplifies the signal transmitted by the mobile phone, and is amplified and passed through the uplink antenna, and is transmitted to the repeater station, and the downstream amplifier turntable issues the signal. The signal is amplified and sent to the handset via the downstream antenna. The upstream amplifier has a large input, and the output frequency selective filter allows only the signal of the operating frequency emitted by the handset to pass. The frequency selective filter of the downstream amplifier only allows the operating frequency signal transmitted from the transmitter (Shanxi Jizhou Electric) to be transmitted. Repeater is very effective in solving dead zone communication in radio communication.
The solution to blind zone communication is basically these two methods. When undertaking such communication projects, signal field strength measurements and engineering calculations must be performed to determine where the main turret is to be placed, the power distribution of each tier and whether or not to add a direct writer, and how to install Repeater and a series of problems, and then choose the equipment to install and debug. In general, this method is usually adopted to solve such blind zone communications. The important one is how to use the actual concrete project, and of course, formal and experienced companies must be selected.
Small computer system interface (SCSI) is an independent processor standard for system level interfaces between computers and intelligent devices (hard disks, floppy drives, optical drives, printers, scanners, etc.). SCSI is an intelligent universal interface standard.
1. SCSI can support multiple devices, SCSI-2 (fastscsi) can connect up to 7 SCSI devices, and widescsi-2 can connect 15 SCSI devices. In other words, all devices only need to occupy one IRQ. At the same time, SCSI also supports a wide range of devices, such as CD-ROM, DVD, CDR, hard disk, tape drive, scanner, etc.
2. SCSI also allows one device to transfer data and another device to look up its data. This can achieve higher performance in multitasking operating systems such as Linux and windows NT.
3. SCSI occupies a very low CPU, so it has obvious advantages in multitask system. Since the SCSI card itself has a CPU, it can handle all the transactions of SCSI devices. When the host CPU sends work instructions to the SCSI card, the SCSI card will work by itself. After the work is finished, the work results will be returned to the CPU. In the whole process, the CPU can carry out its own work.
4. The SCSI device is also intelligent. The SCSI card can queue CPU instructions by itself, which improves the work efficiency. In multitasking, the hard disk will be in the current head position, and the adjacent tasks will be completed first and then processed one by one.
5. The fastest SCSI bus has a bandwidth of 160MB / s, which requires the use of a 64 bit 66MHz PCI slot. Therefore, the maximum speed that can be achieved in the PCI-X bus standard is 80mb / s. if it is used with a dedicated hard disk with 10000rpm or 15000rpm, it will bring obvious performance improvement.
SCSI-180°DIP Section
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