METHOD AND CIRCUIT FOR GENERATING STOP SIGNAL SELECTING BROADCASTING STATION AUTOMATICALLY BY UTILIZING APPLICABLE AFC SIGNAL

摘要

PURPOSE: To allow generation of arrested signal of the automatic selection of a broadcasting station by exclusively using an AFC signal generated by an AFC circuit existing at a receiver. CONSTITUTION: The AFC signal generated by the AFC circuit of the receiver is added to the input of four comparators I to IV. The 1st comparator I having a switchable threshold value is switched if the AFC signal reaches a larger level than two set limit values of the switched threshold value, i.e., when it becomes VA'AFCVA", and the 2nd comparator II having the fixed threshold value V1 between two limit values VA' and VA" of the switched threshold value of the 1st comparator I is activated. If this 2nd comparator II switches, the generation of the arrested signal of automatic selecting scan in which the true presence of a carrier is thus detected on the AFC signal characteristic is decided by an output buffer. Thus, the desired output signal easily usable to arrest the automatic selecting scan is obtained.