Lighting company Dialight reported a drop in underlying operating profit for the first half, reflecting the repositioning of its obstruction signals business.The group said profit fell to £5.5m from £8.2m in 2012, as sales of obstruction signals declined by 40%. Underlying earnings per share slid to 11.6p from 17.3p."The major reason for the decline in US Obstruction sales has been a complete change of channel and product strategy precipitated by the termination of Dialight's relationship with its former principal distribution partner in this business," Dialight explained.Nevertheless, group revenue from continuing operations rose to £59.9m from £53.1m, driven by the lighting segment business which achieved a 70% increase in sales. The division was supported by a £3.0m investment in two new manufacturing facilities in Malaysia and Mexico and in funding the Airinet lighting controls development team in the US.The firm ended the period with net cash of £11.2m, up from £8.1m last year, and increased its interim dividend by 22.5% to 4.9p from 4.0p."The first half has seen strong performance from our lighting segment with excellent growth," said Chief Executive, Roy Burton. "This gives us further confidence in the prospects of our ongoing strategy."RD