Error Rates and Error Distributions on Data Transmitted Over Switched Telephone Connections

This paper describe's the results of tests which have been carried out in order to collect material with respect to errors caused by interference during the transmission of data. The tests have been carried out on a variety of local and toll switched telephone connections at 250, 500, and 1000 bauds. The signal has been set at various levels between -6 dbmo and -46 dbmo. Frequency modulation using only a portion of the available bandwidth has been employed so that a return path can be provided for signals in the reverse direction. Statistics are included in respect to data blocks of 50, 100, 200, and 500 bits. The attenuation-frequency characteristics of a number of test connections are given as both mean and extreme measurements. Many of the tests described were made before the issue of the Test Program drawn up by Working Party 43 of the CCITT in March, 1960, but in most important respects all the tests are in agreement with the procedure recommended.