Digital Security Controls PC1575 Installationshandbuch PDF herunterladen (Seite 104)

computers have two serial ports; one for a mouse and one for a modem or serial

printer. Serial ports are identified by their shape and connection pins. They are

sometimes called “D” type connectors because they are roughly shaped like a “D”.

Parallel printer connectors can sometimes be confused for a serial port because

they have similar shape and dimensions, however they can be identified by the

gender of the connector. Serial ports always have MALE pins on the computer end,

therefore the cable must be female. Parallel ports, on the other hand, are always

FEMALE connectors, therefore the printer cable must be male.

If you have an INTERNAL modem, it is not necessary to have a serial port, because

the modem itself effectively becomes a serial port. Internal modems are installed

inside your computer and plugged into an expansion slot. Make sure that you

have plugged it into the correct type of expansion slot (one that is the right size).

If your computer already has two serial ports, it may not work properly if you add

a third port. If this is the case, you may have to disable one of the serial ports. The

easiest way to do this, is to unplug the device in one of the ports. Check your

modem DIP switches to set it to the proper COM Port (COM1, COM2, COM3 or

COM4). An explanation of the DIP switches (sometimes called Configuration

switches) can be found in your modem manual. If you do not have a modem

manual, you can try calling the manufacturer of the modem, or the store that sold

you the modem. If this is not possible, then you may have to use a trial-and-error

approach with the DIP switches.

NOTE: You must use the first available COM port. (eg. if COM1 & COM2 are used,

you must use COM3. COM4 will not function unless COM1 and COM2 and COM3

are present and/or used.)

7 Check the Phone Jack Type. All modems designed for use in North America allow

for the RJ11 telephone jack. RJ11s have at least two wires and sometimes four.

Some phone connection cables only support the use of two wires under the

assumption that most users only have one phone line. If your cable only has two

wires, it could cause a problem because some modems require all four wires. If this

is the case, then switch to a four wire cable, and it may solve this problem. If you

have two phone lines, it is possible that signals may leak from one line into the other,

causing errors in transmission. If you suspect this is a problem, your phone

company can usually install a filter on your lines, although make sure you get the

right kind of filter installed on the lines because there are filters for voice lines and

filters for data lines. If the wrong type of filter is installed, it could make your

problems worse. Some modems, although they may have four wire jacks, may only

support the use of only one pair of wires, and could mean you may have to switch

the wires in the jack box. If you have more than two phone lines, the jack type will

be different (possibly an RJ12 or RJ13 jack) and you will have to change the DIP

switches on your modem to accommodate this.

8 Check the Modem Cable. If your modem cable came with the modem you bought,

then it is probably the right one, but if it is a cable that you may have had around

for a while, you should check the connectors. Modem cables look a lot like printer

cables and are often mistaken for one another. The main difference between them

is that a modem cable is male on one end and female on the other, therefore you

could plug the ends into each other, whereas a printer cable usually is male at both

ends or has a Centronics (slot) type connector at one end. If the shape and size

of the connectors are not the problem, then check for the number of pins on the

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