Vcrtape.83p - VCR Tape Counter / Time Conversion.

     Do you have a VCR that has a number counter instead or telling you the playing time? Isn't it frustrating trying to find the beginning of the next program or cuing to a specific point in a movie? Not any more, you can calculate the time +/- a minute or so easily and quickly.

     Since the tape reel surface area is a linear function of the length of tape (time) and tape count (reel revolutions) is a linear function of the radius of the tape reel, their relationship can be calculated.

Necessary information:
1. Counter number at the end of tape (an index of tape reel revolutions)
2. length of the tape (in minutes)
3. radius of empty tape reel (avg. tape is 12.8mm)
4. Radius of full tape reel (avg. tape is 39.1mm for T-120 tapes)(avg. tape is 41mm for T-160 tapes)

Adjustments to program for your VCR: counter number, tape length, and tape speed:

Counter Number: 
The first line of the program (5925/(39.1-12.8)->J) is the max count of your tape counter. In this example it is 5925 for my Panasonic VCR. divided by the radius of full tape reel (39.1) minus the radius of the empty reel (12.8), and is stored in variable J.
*Be sure to set the COUNTER NUMBER and the RADIUS OF A FULL TAPE REEL to match your tape. To find your counter number: put tape in player, reset counter, fast forward to end, the count displayed is the count for that tape (T-120 or T-160).
Radius of full tape reel 39.1mm for T-120 tape or 41mm for T-160 tape.

Tape Speed: 
The second line (370/((39.1 squared)-(12.8 squared))->K) is the tape length in minutes divided by the square of the radius of the full reel minus the square of the radius of the empty reel and is stored in variable K. The LENGTH of tape AND RADIUS of the full reel must be set for the speed mode and tape type (T-120 or T-160) you are using.
Find your length below:
T-120 tapes
	123 minutes at standard speed 	- (2 hour mode) 
	246 minutes at long play speed 	- (4 hour mode)
	370 minutes at super lp speed 	- (6 hour mode)
T-160 tapes
	163 minutes at standard speed 	- (2 hour mode) 
	326 minutes at long play speed 	- (4 hour mode)
	490 minutes at super lp speed 	- (6 hour mode)