Busy Lamp Field is a feature that allows monitoring the working status of other extensions or cases through pre-configured indicators of an IP phone. MyPBX now tolerates BLF to subscribe the government of PSTN and GSM trunk. A solid lettuce BLF indicator intends the propagation or the stem is free. A solid red show says busy. A flashing red indicator tells you the expansion or the stem is ringing. The aspect needs both IP phone and MyPBX to support.As an portrait, we use IP phone of extension 500 to monitor extension 501 and stalk pstn1. Log in the Web interface of the IP phone. Extension 500 is registered on Line 1 of the IP phone. Click “Phone” and “DSS Keys”. Use DSS Key 1 to monitor extension 501. In the pull down list of Type, pick BLF. Fill in 501 in the quality domain. Choose the line that postponement 500 is registered to for Line. In the field of Extension, open the feature code of call pickup and the expansion digit, i.e. asterisk 04501. Next, we use DSS Key 2 to monitor trunk pstn1. In type, also select BLF, the “Value” is the name of the stem that is to be monitored. Choose Line 1 and leave the extension field blank. Save the defines. From the BLF indicators of extension 500, we can see that when expansion 501 is free, the DSS Key 1 indication is green, when 501 doughnuts, the indicator blinks red, and when 501 picks up, the indicator demonstrates solid red. In add-on, when 501 sounds, we can press the DSS Key 1 to pick up the call.When the call is picked up, the indicator turns green, sense 501 is idle. Monitoring trunks is almost the same as monitoring extensions, except that there is no call pickup function but the checked stalk is gonna be directly picked. If pstn1 is free, and when we press DSS Key 2, we will have dial flavor. In such cases, increase 500 can directly calls out through this trunk without parallel any outbound roadway. Note that this method exclusively works for PSTN trunk but not GSM trunk ..