With the operation of character select keys, alphanumeric data stored in a ROM are successively read out and latched in a latch circuit under the control of a CPU. The call sign data of a received channel assembled in the latch circuit are stored together with the frequency data of that received channel...http://www.google.de/patents/US4392246?utm_source=gb-gplus-sharePatent US4392246 - Broadcast wave receiving system
