On {HEAD ~ receipt} of {TAIL ~ a request} related to picture display from a user terminal, a central device transmits an instruction to the plurality of distribution devices and to the plurality of receiving devices, according to a usage condition of the transmission line and the number of simultaneously distributed pictures 
On { HEAD ~ receipt } of { TAIL ~ a request } related to picture display from a user terminal , a central device transmits an instruction to the plurality of distribution devices and to the plurality of receiving devices , according to a usage condition of the transmission line and the number of simultaneously distributed pictures
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