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") ![](/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](/en/request-information "Write to us") ### Busy Lamp Field (BLF) [Busy lamp fields and associated function keys](/en/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](/en/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](/en/get-started/cloud-telephony/lexicon/knowledge-base-detail/busy-lamp-field-blf#section-5) 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](/en/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](/en/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](/en/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) [Fixed Mobile Convergence (FMC)](/en/get-started/cloud-telephony/lexicon/knowledge-base-detail/fmc) [Back](#) ![NFON Logo](/assets/logo-nfon.svg) News * [Events](https://www.nfon.com/en/news/events) * [Press](https://corporate.nfon.com/en/communication/) Customers * [Cloudya Login](https://start.cloudya.com/auth/login) * [Admin Portal](https://admin.nfon.com/) * [NFON Status](https://status.nfon.com/) About NFON * [Corporate](https://corporate.nfon.com/en/) * [Investor Relations](https://corporate.nfon.com/en/investor-relations/ir-at-a-glance/) * [Sustainability & ESG](https://corporate.nfon.com/en/sustainability/) * [Career](https://corporate.nfon.com/en/careers/) Legal * [GTC-SLA](/en/legal/gtc-sla) * [Legal Notice](/en/legal/legal-notice) * [Trust Center](https://www.nfon.com/en/trust-center/) * [Data Protection](/en/legal/data-protection) * [Cookie Settings](javascript:onclick=UC_UI.showSecondLayer()) © 2026 - NFON | All rights reserved.