Bintec-elmeg 5510000272 is a key extension module that expands the elmeg S530 or elmeg S560 system phones by 30 freely programmable keys (function and dial keys). Each key can be used in 2 levels and has 2 LEDs for status information, e.g. to show the busy status of employees. A system phone can be expanded by up to three T500 modules - and can therefore be completed to a complex communication center.