RS232 serial cable pinout
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[edit] RS232 - serial cables pinout configuration (wiring)
[edit] Null Modem Type
Null Modem Type is the most common type of wiring for serial cables (~95%).
The bad thing about null modem wiring is that it comes in 4 flavours: http://www.lammertbies.nl/comm/info/RS-232_null_modem.html#full
[edit] Serial Cables
In order to properly connect the computer to the PBX unit you need to know what kind of serial port do you have on you computer. The serial port connectior can be of 2 types: with 9 pins and with 25 pins. The 9 pins are more common and ussualy are used for mouse.
Image:Pbx db25female.png Image:Pbx db9male.png
Look for the following types of connector on the back of your PC. If you don't have a free one you should buy an mouse for PS/2 or USB in order to make one free. Be carefully that the printer port looks it's an DB25 male connector and can't be used.
Next step is to find the PBX serial port. If you are lucky you find it on quickly on PBX unit but in some cases the unit doen't have a connector for the serial port and you must connect the wires directly on the board.
Note down what kind of connector do you have an the PC side and what kind of connector do you need on the PBX. Now you can go to buy the right serial cable if don't have one. Making serial cables
Rule #1: I you are not sure what you are going to do, go an buy a cable and you'll save same time and maybe a lot of money. (it's easy to burn your serial interface if you are makeing a wrong cable!)
Rule #2: The serial cable should be as short as possible and up to 14 meters (50 ft).
You'll need: two serial connectors, a cables with 3-8 wires (you can use UTP or telephony cable), shielded is better, a soldering iron and some experience.
Thease are the pin connections used for serial connection. For Panasonic PBX units use one of them.
| PBX | PC |
| DB25 | DB25 |
| 1 | 1 |
| 2 | 3 |
| 3 | 2 |
| 5+6 | 20 |
| 7 | 7 |
| 20 | 5+6+8 |
| PBX DB25 | PC DB9 |
| 2 | 2 |
| 3 | 3 |
| 4 | 8 |
| 5 | 7 |
| 6 | 4 |
| 7 | 5 |
| 20 | 6 |
^PBX DB9^PC DB9^ |2| 3| |3| 2| |4| 6| |6| 4| |5| 5| |7| 8| |8| 7|
^PBX DB9^PC DB25^ |2| 2| |3| 3| |4| 5+6+8| |5| 7| |6+8| 20|
[edit] Siemens Cable format (own standard)
^PBX DB25^PC DB9^ |2| 2| |3| 3| |5| 7| |4| 8| |7| 5| | |1+4+6|
^PBX DB25^PC DB25^ |2| 3| |3| 2| |5| 4| |4| 5| |7| 7| | |6+8+20|
[edit] Installing the serial cable
There are some other rules you need to follow:
- Don't connect or disconnect the cable while the devices are powered.
- Keep the cable away from the radio signals especially from the GSM equipments because the give a very big noise and you'll loose data. The GSM equipments but be at least 3 meters away from the serial cable.
- Keep the cable as short as possible
- Use a screwdriver to lock the cables into the connectors because someday, someone will stumble on your cable.
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