Abstract: The present invention provides for a method of manufacturing a filter assembly having a filter frame member (402) and the filter assembly (500) produced thereby. The method includes the step of supporting a filter media (202) preferably using a pair of support members (102 and 204). The support members (102 and 204) hold the filter media in place and allow portions of the filter media (202) to be exposed around the media's periphery. Next, a filter support frame (402) is placed around and in proximity to the exposed filter media. The filter support frame (402) is then welded, preferably ultrasonically, to the exposed portions of the filter media. Once welded, the pleated filter assembly is removed from the support members (102 and 204).

Abstract: A data communications system, e.g. for "hands free" personnel location or access control, comprises a master transceiver and a plurality of slave transceivers for transmitting individual identification messages to the master in accordance with a code in which binary values are represented by an infra-red transmission occuring during a first portion or a second portion of a bit period respectively. The master alternately echoes back to the slaves a binary value corresponding to the value last received. In the event of a clash, however, i.e. different values transmitted from different slaves during the same bit period, the master echoes back only a predetermined single value and the slave(s) which did not transmit that value then cease transmission. This process continues until one of the slaves has transmitted and had echoed back bit-by-bit the whole of its message.