referring first to fig1 there is illustrated at 10 a conventional baseball playing field , with the first and third base lines being designated 11 and 12 respectively and meeting at home plate 13 . the bases are shown at 14 , and the three outfielders are represented diagrammatically at 15 ( left fielder ), 16 ( center fielder ), and 17 ( right fielder ). the three fielders carry three separate receiving units or fielders units 18 , 19 and 20 , which receive signals from two control units 21 and 22 carried by two coaches 23 and 24 typically located near the third and first base lines respectively . fig3 shows in enlarged form the control unit 21 and the two fielders units 18 and 19 associated therewith . the second control unit 22 is constructed the same way as unit 21 except that the radio signals emitted thereby are of a character to be received only by the two fielders units 19 and 20 , rather than units 18 and 19 . as seen in fig3 control unit 21 includes a housing 25 which is small enough to be held in the hand of a coach or other person sending signals to the outfielders , and which has a first pair of manually actuated elements 26 and 27 for sending signals to left fielder 15 , and a second pair of manually actuated elements 28 and 29 for sending signals to the center fielder 16 . the elements 26 , 27 , 28 and 29 may be push - buttons , or as illustrated may be elongated bars which are manually depressable relative to the housing 25 . depression of any of the elements 24 , 25 , 26 or 27 actuates a corresponding electrical switch 30 , 31 , 32 or 33 in housing 25 . a first radio transmitter 34 within housing 25 , energized by a battery 35 within the housing , acts to transmit radio signals from an antenna 36 to receiving antennas 37 and 38 of unit 18 carried by the left fielder . a second similar transmitter 39 transmits radio waves from an antenna 40 of unit 21 to receiving antennas 41 and 42 of the center fielders unit 19 . the radio signals transmitted from antennas 36 and 40 are of four different types for the four control elements 26 , 27 , 28 and 29 respectively , and are recognized and received individually by the units 18 and 19 . that is , the radio signal emitted from antenna 36 when element 26 is pressed is different than the signal emitted when each of the other elements 27 , 28 and 29 is pressed , and similarly the signal produced by depression of element 27 is different than each of the three other signals produced when elements 26 , 28 and 29 are actuated , etc . for example , the four signals produceable by unit 21 may be of different frequencies recognizable by units 18 and 19 . referring now the upper portion of fig3 the fielders unit 18 includes a housing 43 which is adapted to be attached to a wearer &# 39 ; s uniform , typically at the front of his shirt as illustrated in fig2 and 4 . for this purpose , the back of housing 43 may have pins 44 or other fastening elements for securing the unit to the shirt . contained within the housing , there may be a battery 45 energizing two radio receivers 46 and 47 , which are tuned to receive only signals of the particular characteristic frequencies emitted when elements 26 and 27 respectively are depressed . the center fielders unit 19 is constructed the same as unit 18 , having a battery 48 and two radio receivers 49 and 50 within a housing 51 , but with the two transmitters 49 and 50 being tuned to receive and respond to the radio signals transmitted by antenna 40 when elements 28 and 29 respectively are depressed . each of the receivers 46 , 47 , 49 and 50 acts when its corresponding characteristic radio signal is received to energize an associated electric lamp 52 , 53 , 54 or 55 , and an associated buzzer , bell , or other sound producing unit 56 , 57 , 58 , or 59 . the light produced by lamps 52 and 54 may be of a first color or characteristic ( typically red ), to indicate to that particular fielder that he is not to attempt to field a certain ball , while the other two lamps 53 and 55 may be of another color or characteristic ( typically green ), to indicate that the carrying fielder is to make the play . similarly , the sound produced by each of the units 56 , 57 , 58 and 59 can be different than the other three units , to be audibly discernable for indicating whether the particular fielder is or is not to make the play . it is contemplated that in some instances only the visual signal producing units may be employed , or only the audible signal producing units may be employed , or alternatively other types of units producing sensible signals may be provided , such as for example vibrators or the like which when operated may be felt by the fielder . as seen in fig4 the lamps 52 , 53 , etc . may be carried by units 18 or 19 in a manner directing the emitted light upwardly toward the face of the fielder , and a light reflective surface , such as a layer of white cloth or a light , may be provided at the underside 60 of the bill 61 of each players &# 39 ; cap 62 . this surface 60 can then reflect the upwardly directed red or green light back toward the eyes of the player , to assure that he receives the visual signal . the second control unit 22 at the second side of the playing field acts upon depression of two of its control elements 26 and 27 , or 28 and 29 , to emit two characteristic radio signals , having the same frequencies as are produced by depression of elements 28 and 29 of unit 21 , to thereby transmit signals to the same center fielders unit 19 as are sent from one side of unit 21 . the other two frequencies emitted by the second control unit 22 are entirely different than the signals produced by any of the elements of unit 21 , to be receivable only by the right fielders unit 20 , to indicate to him whether he should or should not make a play . describing now a cycle of use of the units 18 , 19 and 21 of fig3 assume that a ball has been batted to a location between the center fielder 16 and left fielder 15 , and that these two fielders are not readily able to tell for themselves which should make the play on the ball . as soon as the coach 23 is able to determine from his vantage point which of the fielders has the best opportunity of reaching the ball , he presses appropriate ones of the elements 26 to 29 to communicate appropriate instructions to fielders 15 and 16 . if he feels that fielder 15 should make the catch , the coach presses elements 27 and 28 of unit 21 in fig3 . depression of element 27 throws a switch 31 to cause energization of transmitter 34 to emit from antenna 36 a receiving signal to which only the radio receiver 48 is tuned . the signal is received by that receiver 47 and causes illumination of lamp 53 and energization of sound producing unit 57 to indicate to fielder 15 that he is to make the play . depression of element 28 similarly causes transmission of a radio signal of a characteristic frequency from antenna 40 , to which signal only the receiver 49 is tuned , to cause energization of lamp 54 and sound producing unit 58 indicating to center fielder 16 that he is not to make the play . if the center fielder is the one who should make the catch in a particular situation , the elements 26 and 29 are pressed , to give the green light to the center fielder and the red light to the left fielder . when the ball is between the center fielder and the right fielder , the second coach 24 similarly actuates the appropriate pressable elements of unit 22 , to transmit a go - ahead radio signal to one of the fielders 16 or 17 , and a contrary signal to the other fielder . in the variational fig5 arrangement , a single control unit 21a is provided , having six manually depressable elements 26a arranged in three pairs for sending radio signals of six different frequencies to the three fielder units 18a , 19a and 20a corresponding to units 18 , 19 and 20 in fig1 . one coach may thus hold the unit 21a , and actuate appropriate ones of the elements 26a to give to each of the fielders a sensible signal to either make the catch or hold back and allow another player to field the ball . while certain specific embodiments of the present invention have been disclosed as typical , the invention is of course not limited to these particular forms , but rather is applicable broadly to all such variations as fall within the scope of the appended claims .
apparatus for preventing injury to fielders , including control means to be actuated by a coach or other person or persons , and separate fielder units to be carried by different fielders and adapted to receive radio signals from the control means and produce signals which can be sensed by the fielder to indicate to him which of the fielders is nearer to the ball and should field it .