Textile signal lines (TSLs) are important elements of the clothing of the future, i.e. smart clothing or e-textiles. The goal of the analysis described in this article is to check the possibility of fabricating a microstrip, coplanar and grounded coplanar TSL with a characteristic impedance of 50 ohms or less, using flat fabrics. Lines with this impedance are often used in various transmission systems, e.g. to connect a radio transmitter with an antenna. The analysed and tested lines were made of available flat textile materials. Electro-conductive tracks of the textile line were made of an electro-conductive fabric sewn onto a non-conductive textile substrate. The article presents the results of theoretical analysis and measurements of the characteristic impedance of the real TSLs.