The Women's Emergency Signalling Corps was founded by Florence Violet McKenzie in 1939. As World War II loomed, McKenzie saw that with her qualifications and teaching skills she could make a valuable contribution. She foresaw a military demand for people with skills in wireless communications. As she told The Australian Women's Weekly in 1978: "When Neville Chamberlain came back from Munich and said 'Peace in our time' [sic], I began preparing for war."
In 1939 McKenzie established the Women's Emergency Signalling Corps in Sydney in her Clarence Street rooms – known affectionately as "Sigs". Her original idea was to train women in telegraphy so that they could replace men working in civilian communications, thereby freeing those skilled men up to serve in the war. By the time war broke out, 120 women had been trained to instructional standard.
However, it quickly became apparent that men in the armed forces also urgently needed training in wireless communications and McKenzie's female trainees were in a position to train the male servicemen directly:
Early in the war, one young would-be pilot tried to enlist but was refused because he didn't know Morse code…By sheer coincidence he walked past [the Women's Emergency Signalling Corps on Clarence Street] and heard the sounds of Morse signalling. "It was just a room full of women", remembered Mrs McKenzie, "but he walked up to me and said 'Will you teach me Morse code?' I just heaved a big sigh because I saw a whole world opening up in front of me. Then I knew what we could do. We could train girls to train the men. It was wonderful, because I'd thought we could only do things like relieving in the post office."
The premises at 9 Clarence Street became overcrowded, so McKenzie moved the operation to an old wool store at 10 Clarence Street, where for the next decade the WESC occupied the first and second floors, which she renovated with linoleum flooring and installed radio equipment for twelve classes. Sometimes military intelligence personnel would appear at the school with complaints from guests in the pub next door, who thought a spy operation was at work when they heard Morse code through the walls each evening.
McKenzie ran the school without any government grant or allocation of accommodation by the services. The women of the WESC each gave one shilling per week towards the rent. No fees were ever charged for tuition as McKenzie said it was "her contribution to the war effort". By August 1940, there was a waiting list of 600 women for the small school, and WESC-trained telegraphists were teaching men from the armed forces and merchant navy.