A description is given of a bollard designed specifically for signalling in places through which, road traffic passes, both in cities, towns and villages and on roads and motorways. The transceiver includes a clock data recovery circuit recovers a receive clock signal and outputs a reference clock signal. Accordingly, fewer additional optical elements are required for control of input paths in the beam-combining unit. The reaction of the amino-siloxane compositions provided by the present invention with carbon dioxide is reversible and thus, the method provides for multicycle use of said compositions.