100 	XLIST	ON
 110 	EXTEND=	JMS I	[XTEND]	/SIGN EXTENSION
 120 	LOAD=	JMS I	[XLOAD]	/LOAD A WORD
 130 	M=	D-1		/MASK FOR TIME FORMULAE
 140 	MARK=	JMS I	[MARKER]/MARK A POINT ROUTINE
 150 	NEXTX=	JMS I	[XNEXTX]/BUMP TO NEXT X POINT
 160 	NEXTY=	JMS I	[XNEXTY]/BUMP TO NEXT Y POINT
 170 	NL0002=	CLA CLL CML RTL	/LOAD AC WITH 0002
 180 	NL0004=	CLA CLL IAC RTL	/LOAD AC WITH 0004
 190 	NL3777=	CLA CLL CMA RAR	/LOAD AC WITH 3777
 200 	NL7776=	CLA CLL CMA RAL	/SET AC TO 7776
 210 	SCANIN=	JMS I	[SCAN]	/SCAN IN FIRST ROUTINE
 220 	SCANOUT=JMS I	[SCAN2]	/SECOND SCAN ROUTINE
 230 	STORE=	JMS I	[XSTORE]/STORE A WORD
 240 	EJECT
 250 	*17				/DEFINE PAGE ZERO LOCATIONS
 260 
 270 XR1,	.-.				/AUTO-INDEX NUMBER ONE
 280 
 290 ADDFLAG,.-.				/ADD ON OFF2 FLAG
 300 ADDRESS,.-.				/ADDRESS TEMPORARY
 310 BEGFDG,	T=	FUDG1&M^12+FUDG1F%D	/BEGINNING
 320 	FUDG1%D^12+T;	0		/RELOCATION FACTOR
 330 BEPTR,	ZBLOCK	2			/BLINK END POINTER
 340 BLIMIT,	.-.				/LIMITING BLOCK NUMBER
 350 BLINK1,	T=	BLNK1&M^12+BLNK1F%D	/END OF BLINK
 360 	BLNK1%D^12+T;	0		/UP TO DOWN TIME
 370 BLINK2,	T=	BLNK2&M^12+BLNK2F%D	/DEFINITE END
 380 	BLNK2%D^12+T;	0		/OF BLINK TIME
 390 BLINK3,	BLNK3				/BLINK BEGIN THRESHOLD
 400 BLINK4,	BLNK4				/BLINK END THRESHOLD
 410 BLKDF1,	BLDIF1				/BLINK VERTICAL BEGIN THRESHOLD
 420 BLKDF2,	BLDIF2				/BLINK VERTICAL END THRESHOLD
 430 BLNKCT,	.-.				/BLINK LIMITING COUNT
 440 BLUPDAT,T=	UPDAT&M^12+UPDATF%D	/BLINK
 450 	UPDAT%D^12+T;	0		/UPDATE FACTOR
 460 BPTR,	ZBLOCK	2			/BEGIN POINTER
 470 BUFF1,	.-.				/TEMPORARY
 480 BUFF2,	.-.				/TEMPORARY
 490 DFF1,	DIFF1				/HORIZONTAL BEGIN THRESHOLD
 500 DFF2,	DIFF2				/VERTICAL BEGIN THRESHOLD
 510 DFF3,	DIFF3				/HORIZONTAL END THRESHOLD
 520 DFF4,	DIFF4				/VERTICAL END THRESHOLD
 530 DPM1,	-1;	-1			/7777 7777
 540 DP2,	2;	0			/0000 0002
 550 ENDFDG,	T=	FUDG2&M^12+FUDG2F%D	/ENDING
 560 	FUDG2%D^12+T;	0		/RELOCATION FACTOR
 570 EPTR,	ZBLOCK	2			/END POINTER
 580 MQSAVE,	.-.				/MQ SAVED HERE
 590 MRKTEM,	.-.				/MARKER TEMPORARY
 600 OFFSET,	T=	TIME1&M^12+TIME1F%D	/MEDIAN TIME DIFFERENCE
 610 	O=	TIME1%D^12+T;O;	0	/FOR BEGINNING
 620 OFF2,	T=	TIME2&M^12+TIME2F%D	/MEDIAN TIME
 630 	T=	TIME2%D^12+T		/DIFFERENCE
 640 	T-O;	T-O%4000^7777		/FOR END
 650 	EJECT
 660 PTR,	3-CHAN;	0			/SCAN POINTER
 670 STORFLG,.-.				/BUFFER DIRTY SWITCH
 680 TAS,	.-.				/TEST AND SET SWITCH
 690 TEMP1,	.-.				/TEMPORARY
 700 TEMP2,	.-.				/TEMPORARY
 710 TEMP3,	.-.				/TEMPORARY
 720 TEMP4,	.-.				/TEMPORARY
 730 TEMP5,	.-.				/TEMPORARY
 740 TIMDIF,	T=	TIME3&M^12+TIME3F%D	/BOUNDARY TIME VALUE
 750 	TIME3%D^12+T;	0		/FOR SLOW-PHASE
 760 TMPTR1,	ZBLOCK	2			/TEMPORARY
 770 TMPTR2,	ZBLOCK	2			/TEMPORARY
 780 TMPTR3,	ZBLOCK	2			/TEMPORARY
 790 	EJECT
 800 	PAGE
 810 
 820 /MAIN-LINE FIND CODE
 830 
 840 START,	JMS I	[SYSIO]		/CALL I/O ROUTINES
 850 A7400,	7400			/TO READ IN
 860 	1^100+UNIT		/FIRST BLOCK
 870 	0			/FOR LENGTH
 880 	TAD I	A7400		/GET THE LENGTH ITSELF
 890 	CIA			/INVERT FOR LATER TESTING
 900 	DCA	BLIMIT		/SAVE IT
 910 	XLIST	OFF
 920 	IFZERO	EAESET	<
 930 	XLIST	ON
 940 	SWBA			/BACK TO MODE A
 950 	0			/IN CASE 8/I
 960 	XLIST	OFF	>
 970 	IFNZRO	EAESET	<
 980 	XLIST	ON
 990 	SWAB			/GOTO MODE B
1000 	XLIST	OFF	>
1010 	XLIST	ON
1020 LEADX,	NEXTX;	PTR		/INCREMENT TO NEXT X
1030 	SCANIN			/SETUP AN X VALUE
1040 	COMPARE			/COMPARE X
1050 	DFF1			/TO THIS
1060 	JMP	LEADY		/BELOW THRESHOLD, TRY A Y
1070 FOUNDX,	STA			/FOUND BEGINNING X,
1080 	MARK			/GO MARK IT
1090 	JMP	TRAILX		/SEARCH FOR AN END POINT
1100 
1110 LEADY,	NEXTY;	PTR		/INCREMENT TO NEXT Y
1120 	SCANIN			/GO SETUP A Y VALUE
1130 	COMPARE			/COMPARE Y
1140 	DFF2			/TO THIS
1150 	JMP	LEADX		/BELOW THRESHOLD, GO TRY AN X
1160 FOUNDY,	STA			/FOUND BEGINNING Y,
1170 	MARK			/GO MARK IT
1180 TRAILX,	NEXTX;	PTR		/INCREMENT TO NEXT X