<P> Although few numbers stations have been tracked down by location, the technology used to transmit the numbers has historically been clear--stock shortwave transmitters using powers from 10 kW to 100 kW . </P> <P> Amplitude modulated (AM) transmitters with optionally--variable frequency, using class - C power output stages with plate modulation, are the workhorses of international shortwave broadcasting, including numbers stations . </P> <P> Application of spectrum analysis to numbers station signals has revealed the presence of data bursts, RTTY - modulated subcarriers, phase - shifted carriers, and other unusual transmitter modulations like polytones . (RTTY - modulated subcarriers were also present on some U.S. commercial radio transmissions during the Cold War .) </P> <P> The frequently reported use of high - tech modulations like data bursts, in combination or in sequence with spoken numbers, suggests varying transmissions for differing intelligence operations . </P>

Where do we use number names in real life