Dial primary phone number for the company. Wait for answer a call and hear a greeting of the answering machine. Usually at the end of the message there is a listing of key extension number, so you will be able to compare that which you have written. Wait until you are offered to gain the necessary shortcode.
Put your telephone in the tone mode set. This is because a PABX is used to redirect a call to a particular telephone that is tone mode. Click on your device button is drawn with an asterisk, which is placed under the main buttons of the set. Also some vehicles have a special button "Pulse-Tone", which switches the phone from one mode to another. Remember that if your device originally worked in the tone mode, there is nothing to switch is not necessary.
Wait a few seconds for the phone to switch to a new mode dial. Enter the extension number you want to call. This will hear short signals of various frequencies, which indicates a successful switching to tone mode.
Wait for a response and verify that the PBX is properly connected you with the right person. There are times when not automatically switching and the system connects you with a different extension number. If such happened, then ask the responding Secretary or any other employee to self-direct your call to the desired extension number. As a rule, to such request are understanding as this problem is quite common.
Do not call an extension number from a mobile phone. First, it is quite expensive because you have to call the landline number. Secondly, the conversation with the answering machine takes sometimes a long time, and the cost of the call comes sometimes when switching to the extension number, so you can be disabled because of the shortage of funds in the account. Thirdly, not all mobile phones allow you to communicate with the extension number that is operating in tone mode.