Automatic record size detector
AssigneeHitachi, Ltd.
InventorsHiromichi Tanaka, Osamu Imamura, Akihiro Asada
Life of this patent
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Abstract
Three sets of light receivers are arranged on the turn table of a phonograph record player. The light radiated on the turn table is received and introduced to light receiving elements for conversion into a pulse signal. When a 30-cm record is placed on the turn table, the three sets of light receivers are all converted and fail to produce a pluse signal. When a 25-cm record is placed on the turn table, the first set of light receivers are exposed; while when a 17-cm record is placed on the turn table, the first and second sets of light receivers are exposed. The number of pulses produced from the light receiving elements is counted, thus determining the size of the record placed on the turn table.
Claims8
An apparatus for automatically detecting one of a plurality of predetermined possible sizes of a disc record, comprising record size detecting means for generating a pulse signal in the form of groups of pulses in which each group has pulses corresponding in number to one of said possible record sizes, first comparator means for producing a control signal when the interpulse time of the pulse signal produced by said record size detecting means exceeds a first set time corresponding to the normal interpulse period between pulses in a pulse group, time measuring means responsive to the output control signal of said first comparator means and said pulse signal for generating an output representing a measuring time period, second comparator means for comparing the measuring time period represented by the output of said time measuring means with a second set time corresponding to the maximum length of a pulse group, counter means for counting said pulses in said pulse signal, said counter being reset by the output of said second comparator means, gate means responsive to the output of said time measuring means for applying said pulse signal to said counter means, and memory means for storing the output signal of said counter means as an indication of said record size.
An apparatus for automatically detecting record sizes, comprising a turntable on which the records of different diameter sizes are to be placed, said turntable having a plurality of light receiving holes passing therethrough from the upper surface to the back surface thereof, each of the holes being located at a different distance from the center of the turntable in accordance with the possible different diameter sizes of the record and the holes being located at positions angularly shifted from each other by a predetermined amount;
- a light detector;
- meansing including a plurality of light receiving elements for sequentially transmitting light from each corresponding hole to said light detector as the turntable rotates to cause said light detector to generate a pulse signal formed of spaced pulse groups each having a number of pulses corresponding to the number of holes not covered by the record placed on the turntable;
- counter means for counting the number of pulses in a pulse group of the signal outputted from said light detector;
- interpulse detecting means responsive to the output pulse signal from said light detecting means for detecting the interpulse period within the output pulse train thereof and for generating a control signal when a period is detected which exceeds a normal interpulse period within a pulse group;
- a gate circuit connected between said light detector and said counter means for passing the output pulse of said light detector to said counter means in response to the control signal from the interpulse detecting means;
- first time setting means connected to the output of the gate circuit for outputting a first reset signal a first predetermined time after detection of an output pulse of said light detector;
- second time setting means for outputting a second reset signal a predetermined second time longer than said first predetermined time after generation of said control signal by said interpulse detecting means;
- supply means for supplying the first and second reset signals to said interpulse detecting means and said counter means respectively;
- and memory means for storing the output signal from said counter means as a signal representing the diameter size of a record on the turntable.
Dependencies are inferred from the claim text.