Narrowband Frequency modulation is used exclusively, so that the capture effect will select the stronger of two transmitters wherever one predominates.
Notable existing vector magnetographs include the IVM at the Mees Observatory in Hawaii, SVM at Udaipur Solar Observatory, India, the SOLIS instrument at the National Solar Observatory (strictly speaking, SOLIS is a scanned spectropolarimeter), and the narrowband filtergraph instrument on the Hinode spacecraft.
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Other types of magnetograph use narrowband filter imaging to produce a measurement of the first few moments of the spectral line, and operate much more quickly: the HMI instrument on board the Solar Dynamics Observatory will produce a vector magnetogram every few minutes.
Wireless Communications Transfer Protocol (WCTP) is the method used to send messages to wireless devices such as pagers on NPCS (Narrowband PCS) networks.