TELETEXT FILTERS A RANGE OF DIP PULSE SHAPING FILTERS FOR TELETEXT SYSTEMS To avoid data errors the fast pulses produced by data generators need to be band limited prior to insertion into a video channel. When conventional low pass filters are used unacceptable time domain ringing of the pulse results. This range of filters is designed to band limit while avoiding this problem. Due to technical and historic reasons three types of filter are in current use. They are based on the Gaussian, Raised Cosine and Cosine Roll-off realisations. Each has a slightly different characteristic. The cosine roll-off type is the only one that band limits the frequency spectrum to 5.5 MHz so ensuring that a 625 line video system is transparent to the pulse. FX055AD FX055BD FX055CD Filter Type Gaussian Raised cosine Cosine Roll-off Attenuation at 5.5 MHz 3.0 dB 5.0 dB 19.0 dB Impedance 75 ohms 75 ohms 75 ohms Temperature Range 0°C to 70°C 0°C to 70°C 0°C to 70°C Aqueous Washable Yes Yes Yes Package DR00110A DR00110A DR00110A © Faraday Technology. As part of continual product improvement the specifications, details and dimensions shown in this publication are subject to change without notice Fara163d Page 1 of 2 Dec-99(A) PACKAGE DETAIL Faraday Technology Ltd. Croft Road Industrial Estate, Newcastle, Staffordshire ST5 0QZ. England. Fara163d Tel: Fax: Email: Web site: Page 2 of 2 + 44 (0)1782 661501 + 44 (0)1782 630101 [email protected] http://www.faradaytech.co.uk Dec-99(A)