The pictures are broadcast at a rate of about 60Hz, which is how fast they need to move for us to see them as a moving, flawless picture.
1	The	the	DET	DT	Definite=Def|PronType=Art	2	det	2:det	_
2	pictures	picture	NOUN	NNS	Number=Plur	4	nsubj:pass	4:nsubj:pass	_
3	are	be	AUX	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	4	aux:pass	4:aux:pass	_
4	broadcast	broadcast	VERB	VBN	Tense=Past|VerbForm=Part|Voice=Pass	0	root	0:root	_
5	at	at	ADP	IN	_	7	case	7:case	_
6	a	a	DET	DT	Definite=Ind|PronType=Art	7	det	7:det	_
7	rate	rate	NOUN	NN	Number=Sing	4	obl	4:obl:at	_
8	of	of	ADP	IN	_	11	case	11:case	_
9	about	about	ADV	RB	_	10	advmod	10:advmod	_
10	60	60	NUM	CD	NumForm=Digit|NumType=Card	11	nummod	11:nummod	SpaceAfter=No
11	Hz	hz	NOUN	NN	Number=Sing	7	nmod	7:nmod:of|16:nsubj	SpaceAfter=No
12	,	,	PUNCT	,	_	11	punct	11:punct	_
13	which	which	PRON	WDT	PronType=Rel	16	nsubj	11:ref	_
14	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	16	cop	16:cop	CheckUPOS=VERB
15	how	how	ADV	WRB	PronType=Rel	16	advmod	16:advmod	_
16	fast	fast	ADV	RB	Degree=Pos	11	acl:relcl	11:acl:relcl	_
17	they	they	PRON	PRP	Case=Nom|Number=Plur|Person=3|PronType=Prs	18	nsubj	18:nsubj|20:nsubj:xsubj	_
18	need	need	VERB	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	16	advcl:relcl	16:advcl:relcl	_
19	to	to	PART	TO	_	20	mark	20:mark	_
20	move	move	VERB	VB	VerbForm=Inf	18	xcomp	18:xcomp	_
21	for	for	SCONJ	IN	_	24	mark	24:mark	_
22	us	we	PRON	PRP	Case=Acc|Number=Plur|Person=1|PronType=Prs	24	nsubj	24:nsubj	_
23	to	to	PART	TO	_	24	mark	24:mark	_
24	see	see	VERB	VB	VerbForm=Inf	20	advcl	20:advcl:to	_
25	them	they	PRON	PRP	Case=Acc|Number=Plur|Person=3|PronType=Prs	24	obj	24:obj	_
26	as	as	ADP	IN	_	31	case	31:case	_
27	a	a	DET	DT	Definite=Ind|PronType=Art	31	det	31:det	_
28	moving	move	VERB	VBG	VerbForm=Ger	31	amod	31:amod	SpaceAfter=No
29	,	,	PUNCT	,	_	31	punct	31:punct	_
30	flawless	flawless	ADJ	JJ	Degree=Pos	31	amod	31:amod	_
31	picture	picture	NOUN	NN	Number=Sing	24	obl	24:obl:as	SpaceAfter=No
32	.	.	PUNCT	.	_	4	punct	4:punct	_
