signal 12 that can be received by the lamp by use of one of the electrodes 13 as an antenna the antenna being connected to the lamp driver as described in connection with fig1 and 2 in fig3 a signal is transmitted from the wall unit to the lamp the reverse may also be possible i e to transmit a signal from the lamp to the wall unit the wall unit may be electrically powered by means of a battery it may be connected to a mains network etc alternatively the wall unit may be powered mechanically such as by energy gained from pressing a button of the unit the user control is in the present figure illustrated by a wall unit the user control may be any type of unit for controlling a lamp the user control may e g be a transceiver box connected to a light control system e g in connection with a light control system of a building in the foregoing it will be appreciated that reference to the singular is also intended to encompass the plural and vice versa and references to a specific numbers of features or devices are not to be construed as limiting the invention to that specific number of features or devices moreover expressions such as u201c include u201d u201c comprise u201d u201c has u201d u201c have u201d u201c incorporate u201d u201c contain u201d and u201c encompass u201d are to be construed to be non exclusive namely such expressions are to be construed not to exclude other items being present although the present invention has been described in connection with specific embodiments it is.