The man, who had taken early retirement, made the anonymous phone calls over a period of several years from his home in Wels before he was caught.
He would research school websites to identify attractive young female teachers and would call the school using a prepaid mobile phone with no caller ID.
He would ask to speak to the young teacher and tell her to stay on the line while he made vile sexual comments - telling her that he had naked photos of her that he would publish on the Internet and in some cases threatening to come to the teacher's house and rape her.
The prosecutor said that 34 teachers had made an official complaint, but that the man had made hundreds of phone calls and that many more young women had in all likelihood been traumatised by his behaviour. The man was convicted of making threats and of attempted aggravated coercion.