Final results of tests investigating the influence of transmission delay

In this paper the results of investigations made in 1967 and 1969 are presented. In 1967, 94 students took part in tests accomplished in the Heinrich-Hertz-Institut (test series 1). On this subject the author reported at the 4th International Symposium on Human Factors in Telephony at Bad Weissee, Germany, 1968. These tests now are completely evaluated. In 1969 another test with a reduced program was made with 238 visitors to the 'Deutsche Industrieausstellung, Berlin' (Industrial Exhibition) to supplement the investigations (test series 2). A brief survey is given here.