Frequently Asked Questions for Interface Cables

Posted on by Joe Miller

Common USB cable solutions:
Question Answer
Can I add USB ports to my Mac or PC? You will need to add a USB controller card to your Mac or PC.
Is it possible network computers with USB to share files and peripherals? You will need a USB “SmartNet” cable.
Can I connect a device that’s more than 16 feet from my hub? You will need an “active” repeater extension cable.
How can I use my USB port to connect to a network? You will need a USB to Ethernet adapter.
How can I use a parallel port printer with USB? You are going to need a USB to parallel (IEEE-1284) converter.
How can I connect my PS/2 mouse and keyboard to a USB port? You will need a USB to PS/2 port converter.
How can I connect a serial device to USB? You will need a USB to serial converter.
How can I share USB devices between computers? You will need a USB switchbox. Don’t forget your cables too!

Wireless Solutions:
Can I mix 802.11 (2Mbps) with 802.11b (11Mbps) products? 802.11 and 802.11b products can exist and operate together on the same network. Unfortunately, not all implementations of 802.11 or 802.11b were done correctly. For the most part it WILL work, but there are exceptions. This is why the Wi-Fi interoperability certification was created.
What does a wireless access point do? In its simplest form, a wireless access point is a bridge between wired Ethernet and wireless Ethernet (802.11b). An access point is not needed for two wireless computers to talk to each other, but it is vital for free communication between wired and wireless networks.
Do I need an access point to connect two wireless computers? No. All wireless cards can be put into an ‘ad hoc’ mode that allows them to communicate directly to each other. An access point is not needed. Use an access point only when you need to bridge your wireless network with your wired Ethernet network.
I am having trouble getting my wireless cards to communicate. If you are using WEP (encryption) try turning it off. Encryption is sometimes hard to get running so you should start with it turned off. Once you get it running, READ THE INSTRUCTIONS again. Lastly, be sure you are not mixing encryption levels.
What is IEEE 802.11? The IEEE 802.11 is a wireless LAN industry standard, and the objective of IEEE 802.11 is to make sure that different manufactures’ wireless LAN devices can communicate to each other. 802.11 provides 1 or 2 Mbps transmission in the 2.4 GHz ISM band using either FHSS (Frequency Hopped Spread Spectrum) or DSSS (Direct Sequence Spread Spectrum)
What is 802.11a? 802.11a the second revision of 802.11 that operates in the unlicensed 5 GHz band and allows transmission rates of up to 54Mbps. 802.11a uses OFDM (orthogonal frequency division multiplexing) as opposed to FHSS or DSSS. Higher data rates are possible by combining channels. Due to higher frequency, distance range is less than lower frequency systems (i.e., 802.11b and 802.11g) and can increase the cost of the overall solution because a greater number of access points may be required. 802.11a is not directly compatible with 802.11b or 802.11g networks. In other words, a user equipped with an 802.11b or 802.11g radio card will not be able to interface directly to an 802.11a access point. Multimode NICs will solve this problem.
What is 802.11b? 802.11b is the first revision of 802.11 standard allowing data rates up to 11Mbps in the 2.4GHz ISM band. Also known as 802.11 High-Rate and Wi-Fi. 802.11b only uses DSSS, the maximum speed of 11Mbps has fallbacks to 5.5, 2 and 1Mbps.
How fast is 802.11b? The IEEE 802.11b standard has a nominal speed of 11 megabits per second (Mbps). However, depending on signal quality and how many other people are using the wireless Ethernet through a particular Access Point, useable speed will be much less (on the order of 4 or 5 Mbps, which is still substantially faster than most dialup, cable and DSL modems).
What is 802.11g? 802.11g is an extension to 802.11b. 802.11g increases 802.11b’s data rates to 54 Mbps and still utilizes the 2.4 GHz ISM. Modulation is based upon OFDM (orthogonal frequency division multiplexing) technology. An 802.11b radio card will interface directly with an 802.11g access point (and vice versa) at 11 Mbps or lower depending on distance range. The distance range at 54 Mbps is less than for 802.11b operating at 11 Mbps.
Can radio signals pass through walls? Transmitting through a wall is possible depending upon the material used in its construction. In general, metals and substances with a high water content do not allow radio waves to pass through. Metals reflect radio waves and concrete attenuates radio waves. The amount of attenuation suffered in passing through concrete will be a function of its thickness and amount of metal re-enforcement used.
What are potential factors that may causes interference among WLAN products? Factors of interference:

  1. Obstacles: walls, ceilings, furniture… etc.
  2. Building Materials: metal door, aluminum studs.
  3. Electrical devices: microwaves, monitors, electric motors.

Solution:

  1. Minimizing the number of walls and ceilings
  2. Antenna is positioned for best reception.
  3. Keep WLAN products away from electrical devices, (like microwaves, monitors, electric motors… etc.)
  4. Add additional Access Points if necessary.
What’s the difference between a WLAN and a WWAN? WLANs are generally privately owned, wireless systems that are deployed in a corporation, warehouse, hospital, or educational campus setting. Data rates are high and there are no per-packet charges for data transmission.
WWANs are generally publicly shared data networks designed to provide coverage in metropolitan areas and along traffic corridors. WWANs are owned by a service provider or carrier. Data rates are low and charges are based on usage. Specialized applications are characteristically designed around short, burst messaging.
What is Direct-Sequence Spread Spectrum Technology – (DSSS)? DSSS spreads its signal continuously over a wide frequency band. DSSS maps the information bearing bit-pattern at the sending station into a higher data rate bit sequence using a “chipping” code. The chipping code (also known as processing gain) introduces redundancy which allows data recovery if certain bit errors occur during transmission. The FCC rules the minimum processing gain should be 10, typical systems use processing gains of 20. IEEE 802.11b specifies the use of DSSS.
What is Frequency-hopping Spread Spectrum Technology – (FHSS)? FHSS uses a narrowband carrier which hops through a predefined sequence of several frequencies at a specific rate. This avoids problems with fixed channel narrowband noise and simple jamming. Both transmitter and receiver must have their hopping sequences synchronized to create the effect of a single “logical channel”. To unsynchronized receivers an FHSS transmission appears to be short-duration impulse noise. 802.11 may use FHSS or DSSS.
How do I secure the data across an Access Point’s radio link? Enable Wired Equivalency Protocol (WEP) to encrypt the payload of packets sent across a radio link.
What is WEP? Wired Equivalent Privacy. WEP is a security mechanism defined within the 802.11 standard and designed to make the security of the wireless medium equal to that of a cable (wire). WEP data encryption was designed to prevent access to the network by “intruders” and to prevent the capture of wireless LAN traffic through eavesdropping. WEP allows the administrator to define a set of respective “Keys” for each wireless network user based on a “Key String” passed through the WEP encryption algorithm. Access is denied by anyone who does not have an assigned key. WEP comes in 40/64-bit and 128-bit encryption key lengths. Note, WEP has shown to have fundamental flaws in its key generation processing.