 attenuation) of a signal, expressed as the ratio of allow auxiliary control functions to be performed, e.g. error two values. The dBm is referenced to one milliwatt. checking, synchronisation, framing. Dedicated line. Usually refers to a private circuit, often non- Convolutional code. Code using redundant bits for checking the switched. information in the previous blocks of data. Delay. The elapsed time between two events, such as between the Corona. The partial discharge in a gas. This can occur in the air sending and receipt of a signal. spaces contained in a transformer insulation and also in the air Delay distortion. The distortion caused in a transmitted signal due in between power distribution lines, leading to interference in to the different frequencies within that signal experiencing electrical circuits. different amounts of delay. Also refered to as group delay Cost plus pricing. A pricing method which adds a fixed profit distortion. margin onto the cost of manufacturing a component or provid- Delta modulation. Digital encoding technique in which the anal- ing a service, to determine its selling price. ogue signal is continually sampled and only the polarity of the Crossconnect switch. A switch used for connecting one trans- signal slope is transmitted. mission path to another. Demand assignment. The assignment of a transmission channel to Crosspoint. A method for connecting two channels together on a a user on demand. The channel is then available for the time the space division basis. It is the method of switching used in the user takes to complete his transmission. (See also fixed assign- older crosspoint analogue switches. ment.) Crosstalk. The interference between information being trans- Demodulation. Translation of the information contained in a mitted on two different transmission medium, located adjacent modulated signal. to each other. Demultiplexer. An device which separates out different signals CT1 Domestic cordless telephone. Uses 4 channels and public from a channel, which were originall