El acceso a la versión del editor puede requerir la suscripción del recurso Access to the published version may require subscription This paper describes Umbra Designer, a novel graphical modelling tool for the visual development of telephony services, from which Java code for the Umbra framework is synthesized. In this way, it is easy to develop ready-to-use services, even by users not familiar with the Java API or the JAIN SLEE standard. We also report on some experiments aimed at measuring the efficiency gain derived from using the graphical tool, compared with coding directly using the Java API.