In the 1930s worries were growing about the availability of useful radio spectrum. At STC's Paris laboratories, Alec Reeves worked on Single SideBand (SSB) radio techniques to reduce the bandwidth of transmissions. It was successfully demonstrated on the Paris-Madrid-Buenos Aires HF radio links, but the era of the slump was not the best time to apply it. Like many of his ideas, it had to wait for the world to catch up. During the second world war, SSB became the universal system for HF point to point radio telephony.