Television receiver connected to a text decoder such as a videotex decoder or teletex (non-interactive videotext) decoder

摘要

In a television receiver with a horizontal and vertical oscillator, which can be switched to different frequencies, and which is used both for receiving HF-modulated TV signals and for displaying videotex pages, in order to avoid flickering effects during text display, a switch to a higher vertical frequency should take place. For this purpose, the horizontal and vertical oscillators are synchronised via a free-running, switchable oscillator circuit of the text decoder, which is synchronised with the received lower frequency synchronisation pulses on receiving HF-modulated TV signals.