USB-EX75
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User’s Manual for USB Extender

Model: USB-EX75

Deyang FOURSTAR Electronic Technology Co., Ltd.

According to USB standard, the length of a USB cable should be 5m at most. The USB extender USB-EX75 independently developed by our company is also called USB line driver or USB line transceiver. It overcomes the host’s limitation for USB cable length and converts the USB signal of the host into differential signal suitable for long-distance transmission first and transmits it through an ordinary data cable. After reaching the remote end, the differential signal is restored to a standard USB signal. With a pair of USB-EX75 extenders, the communication length of USB may be extended to be 75m (in case of full-speed) or 300m (in case of low-speed) without necessity to change the original communication protocol and software. Designed according to industrial standard, the product is extensively applied in fields like industrial automation, computer, USB data acquisition unit, banking, securities, etc.

Main technical parameters:

●    It supports 12Mbps full-speed USB transmission and 1.5Mbps low-speed USB transmission and is compatible with USB V2.0.

●    Automatic recognition of USB High-Speed and USB Full-Speed or USB Low-Speed.

●    Supporting USB control transmission, bulk transmission, interrupts transmission, synchronous / isochronous transmission.

●     It uses the standard Cat5, Cat5e or Cat6 data cable. The maximum transmission distance of a 12Mbps full-speed USB signal is 75m and that of a 1.5Mbps low-speed USB signal is 300m.

●     As a pure hardware solution, it is completely real-time and transparent for USB protocol. It needs no installation of any drivers and supports Windows98/ME/2000/XP/Vista/Server200X/64bit-Vista/Windows and Linux.

●     Power supply source: 5VDC/20mA, supplied via the USB interface of the host.

●    All upstream and downstream USB interfaces are provided with a surge protector.

●    Working temperature: -40~+85℃

●    Relative humidity: 0~95% (without condensed water)

●    External dimensions: 60×26×26 (L×W×H, mm) aluminum profile shielded enclosure

●    Weight: 100g (each piece)

Installation and use of USB-EX75:

Two pieces of USB-EX75 extenders form a set and should be used at the same time, with one inserted into the host’s USB interface and the other into the USB device. The two pieces of USB-EX75 extenders should be connected by a one-to-one data cable just as a USB device is directly inserted into the host’s USB interface.

The allowable maximum length of data cable: it is 75m when a full-speed USB device is used, or 300m when a low-speed USB device is used, or 75m when the communication speed is decreased to the full speed when a high-speed USB device is used.

The figure below shows the external structure of USB-EX75 and the signal definition of the RJ45 socket at data cable port.

The data cable between the two RJ45sockets of the USB-EX75 extenders should be subject to pressure welding with help of the RJ45 crystal plug shown in the figure below.

Matters needing attention in purchase of data cable

There’s lots of low-quality or imitated data cables on the market produced by some manufacturers. These data cables are made of low-quality materials and have large resistances of leads. A majority of data cables are applied in Ethernet. Generally speaking, only four pieces of leads are used. The said manufacturers use low-quality materials to make the other four pieces of leads which are usually not used. The leads have huge resistances (the DC resistances of some 100-meter single-core leads are over 100Ω). The leads of this sort are not real leads at all. And the data cables with leads like this should not be used.

You’d better purchase the data cables produced by famous manufacturers (pay attention to tell authentic products from counterfeit products. For example, a majority of AMP data cables on the market are low-quality counterfeit data cables). A test done for the data cable you want to buy is necessary. For a qualified data cable, the resistance of a 100-meter single-core lead is equal to or smaller than 10Ω (national standard: 8.5Ω/100m). Any data cables exceeding the aforesaid standard are unqualified.

Method to connect the USB-EX75 extender with USB devices consuming larger electric power consumption

After extension of the data cable, the 5VDC power supply outputted via the host’s USB interface will see great voltage drop on the data cable, which will result in voltage drop of such devices with larger electric power consumption and electric power provided via a USB interface, such as USB hard disk and USB CD-ROM, and further in work failure of the devices. It is necessary at this time to plug a commercially available USB HUB with an external power supply onto the USB downstream socket of the USB-EX75 extenders first and inert the device into the USB HUB then. The external power supply of the USB HUB then can provide electric power.

Also, the voltage of the 5VDC power supply outputted from the USB-EX75 extenders will decline and the operations of the USB devices are likely to become unreliable, if the downstream interfaces are overloaded. It is also necessary at this time to plug a commercially available USB HUB with an external power supply onto the downstream USB socket of the USB-EX75 extenders first and inert the device into the USB HUB then. The external power supply of the USB HUB then can provide electric power.

Solutions for frequently questions:

1. What are high-speed USB devices, full-speed USB devices and low-speed USB devices?

Answer: High-speed USB devices transmit data at a speed of 480M, such as USB disks, USB hard disks, USB CD-ROM, etc.

       Full-speed USB devices transit data at a speed of 12M, such as USB printers, scanners, industrial control devices, etc.

       Low-speed USB devices transit data at a speed of 1.5M, such as USB mouses, card readers, USB keyboards, etc.

2. Why high-speed USB devices (such as USB disks and USB hard disks) have decreased speed of file reading or writing after a pair USB-EX75 extenders is used?

Answer: After connected with a pair of USB-EX75 extenders, a high-speed USB device (480M) will have its speed decreased automatically to full speed (12M). That’s why it runs slower than the speed (480M) when it has not been inserted into the host’s USB interface. The distance extension problem at a speed up to 480M cannot be solved at present. The USB high-speed distance extension by tens of meters stated by some manufacturers in their product description is in fact automatic decrease to full speed too.

3. Why devices like USB printers, USB disks, industrial control devices, USB mousse and USB keyboards can all work normally after a pair of USB-EX75 extenders is used, but USB hard disks cannot work?

Answer: It is because devices like USB printers, USB disks, industrial control devices, USB mousse and USB keyboards consume smaller electric power or don’t obtain electric power via a USB bus, thus smaller currents result in smaller voltage drops on the data cables and the devices can obtain enough working power supply after extension. On the other hand, devices like USB hard disks consume larger electric power and obtain electric power via a USB interface, thus larger currents result in larger voltage drops on data cables and the devices cannot obtain enough working power supply after extension. The method to solve this problem is to plug a commercially available USB HUB with an external power supply onto the USB-EX75 extender at the end in connection with the device first and inert the device (such as USB hard disk) into the USB HUB then. The external power supply of the USB HUB then can provide electric power.

4. Why the data cable length fails to meet the technical indicators specified in Product Specification (i.e. 75m for full speed and 300m for low speed)?

Answer: The most common cause for this problem is an unqualified data cable is used. Please check whether or not the resistance of each 100-meter single-core lead of the data cable used is equal to or smaller than 10Ω, whether or not the crystal plug has good pressure welding, whether or not the wires are correctly connected according to their numbers, etc.

5. If a shielded data cable is used, how to handle the shielding layer?

Answer: In order to improve the anti-interference performance, it is necessary when a shielded data cable is used to select two RJ45 crystal plugs of which the shells are covered by a shielding layer respectively and to conduct pressure welding between the shielding layer at both ends of the data cable and the shielding shells of the two plugs.

6. Is hot plugging is allowed?

Answer: Our USB-EX75 extenders allow hot plugging and are provided with surge protectors on all upstream and downstream USB interfaces.

7. Can multiple pairs of USB-EX7 extenders be used in series so that the communication distance of USB interface can be extended more?

Answer: Even if the voltage drop loss is not considered, the multiple pairs of USB-EX7 extenders used in series will still result in a maximum communication distance of 75m for full speed or 300m for low speed, it is therefore unnecessary to do so. It is because that the time sequence, amplitude, direction, speed and protocol of SUB signal are all strictly specified.

You can find the following items in the packing box of USB-EX75 extenders:

USB-EX75 extender: 1 pair (two pcs)

User’s Manual: 1 copy