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[+44 330 383 8000](tel:+443303838000 "+44 330 383 8000") ![](/images/getstarted-writetous-navbar-int_ZY7MOf.webp) ### Write to us Fill out our request form. Our experts will respond as soon as possible. [Write to us](/gb/request-information "Write to us") ### Busy Lamp Field (BLF) [Busy lamp fields and associated function keys](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/busy-lamp-field-blf#section-3) [Busy lamp field as typical function of the personal assistant telephone](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/busy-lamp-field-blf#section-4) [Busy lamp fields for mobile phones in fixed mobile convergence [FMC] environments](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/busy-lamp-field-blf#section-5) # Busy Lamp Field (BLF) With the help of the so-called ‘busy lamp field’ the call status of another telephone can be seen on own telephone. The busy lamp field is a feature of system telephones of intelligent telephone solutions, and it is available in [VoIP](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/voice-over-ip) environments as well. This feature can be physically integrated into a telephone, set up as an add-on module which can be connected to a telephone, or implemented as a software on a PC. The busy lamp field feature should be supported by the [telephone systems](/gb/gb/products/cloudya) or VoIP servers in order to be able to use it. The number of busy lamp fields available on a telephone may vary drastically depending on the type and area of application. ### Busy lamp fields and associated function keys Generally, busy lamp fields are directly linked to the associated function keys. These keys are assigned to individual lamps and can be used for various functions. A steady light or a blinking light can be used to display the status of a telephone set. Often a steady light indicates an ongoing call and a blinking light an incoming call. Depending on this status, a call can be taken or picked up using the associated function key. If the line is free at the moment, it can be called by pressing the function key. In software-based PC solutions, these actions can be triggered by mouse click. ### Busy lamp field as typical function of the personal assistant telephone The busy lamp field is a typical feature in the telephone of a personal assistant. It supports the assistant’s call management and allows transferring calls to the boss, receiving or picking up calls and knowing the current call status in the boss’ office. ### Busy lamp fields for mobile phones in fixed mobile convergence [FMC] environments Busy lamp fields can be used in mobiles or smart phones where the mobile phones are integrated into [fixed mobile convergence](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/fmc) environments. In such cases, the busy lamp field shows the status in the office when an employee is telephoning with his/her mobile phone or smartphone, even if the employee is at an entirely different location. The mobile is linked to the busy lamp field almost like a normal extension. ### Related Articles ### Fixed Mobile Convergence (FMC) The abbreviation FMC stands for the technical phrase Fixed Mobile Convergence and describes the integration of mobile and [fixed-line](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/the-fixed-line-network) communication services within a complete solution. Whilst mobile and fixed-line telephone networks were technically entirely separate until just a few years ago, nowadays they are increasingly merging. It is therefore possible today to reach a modern FMC solution both on a mobile basis with its landline [number](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/national-international-phone-numbers), and on a fixed-line basis using the mobile number. Furthermore, the use of the telephone service is entirely device-independent. Companies that use FMC solutions are therefore more reachable and thus also benefit from the increased efficiency of their personnel. Additionally, costs are also minimised because the most economical type of connection at the respective time can be selected automatically. Mobile devices such as the smartphone or PDA therefore become valuable extension units, also when carried around the office in the trouser pocket. When the user returns to the office from a business trip, their smartphone books them into the internal company network automatically via WLAN. Without the user even perceiving this action they then use the more economical telephone service of the office system and avoid costly [mobile network connections](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/mobile-phone-network). If you are in the GSM network during an ongoing call with the cell phone (FMC) and switch to a WLAN network that is already defined as an access point on the cell phone, the FMC client automatically changes the connection type from GSM to WLAN (seamless handover). Conversely, this is the same. If you are in the WLAN network with your mobile phone during an ongoing call and leave it, there is an automatic handover from the WLAN to the GSM network. The handover is signaled acoustically on the mobile phone, and there may be a brief interruption. As a rule, the caller does not notice anything about the handover. The FMC client can be used with different SIM cards thanks to the "SIM change" function. This is particularly useful when commuting frequently between different countries. Someone who lives in Austria and works in Germany, for example, can use SIM cards for both countries (German providers such as Vodafone and Austrian providers such as Orange) with the FMC client. If you insert a corresponding SIM card into the mobile phone, for which the GSM number has previously been stored in the telephone system, you only have to select "SIM change" in the configuration menu of the FMC client and the FMC client will connect to it automatically the telephone system. While FMC solutions were primarily tailored to consumer households or small office environments due to the WiFi connectivity, small and medium-sized companies will also adapt their network environment in the future and benefit from the advantages of the flexible and resource-saving solutions. The FMC solution from NFON not only enables the office number to be used on WiFi, but also on the move in the GSM network if WiFi is not available. A connection to the telephone system is established simply by making a call. This brings with it several advantages. On the one hand, you can be reached on the go via the landline number, but you can also signal the office number from your cell phone. This means that you only communicate with one phone number and can be reached from anywhere under this number (one-number concept). If you want to save yourself the landline call to connect to the telephone system while on the go, the callback function can be used. You simply tell the telephone system by pressing a button that it should call you back. The system then calls back and a connection to the destination number is established. Domestically, this function is used to shift the costs from the mobile phone user to the company, e.g. B. the employee uses a private mobile phone tariff. When using the callback function, costs arise exclusively on the part of the telephone system, which leads to a clear cost separation. This function can also be useful abroad. As a rule, roaming charges for outgoing calls (outbound) are more expensive than roaming charges for incoming calls (inbound). If this is the case, you can simply use callback to tell the telephone system abroad that it should call you back. This means that there are no expensive outbound roaming costs and you save money. In addition, you can also save money on expensive forwarding from the telephone system to the cell phone: If you leave the office in the evening and activate fixed call forwarding to your private cell phone, all calls to the office number can be forwarded to the cell phone, which means expensive forwarding costs on the part of the telephone system develop. Anyone who uses the NFON FMC solution on their cell phone saves these costs by simply redirecting to the FMC extension and using the reverse callback function. The reverse callback function avoids expensive forwarding fees. When a call comes in, you first get a call from the telephone system and immediately afterwards a connection is established from the mobile phone to the telephone system – the telephone system then merges the connection from the FMC client and the calling connection. No difference to any other connection is noticeable for the call participants. However, it could be that the call setup takes a few seconds. In the case of a landline flat rate on the mobile phone, there are no additional costs. The prerequisite for using the reverse callback function is a data package in the mobile phone contract and the availability of the data network (GPRS, UMTS, etc.) during an incoming call. 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