; HLPEDITS ;--------------------------------------------------------------- ;! Interactive TY table (not UV) editor - internal help ;# TASK TABLE CALIBRATION INTERACTIVE TV-APPL OOP UV EDITING ;----------------------------------------------------------------------- ;; Copyright (C) 2006-2007, 2010 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- C----------------------------------------------------------------------- FLAG TIME This option allows you to flag (delete) the Tsys for a specific time. Move the cursor to the time you wish to flag. The vertical line will follow it while the time and value of the Tsys nearest the cursor will be displayed in the top left corner of the TV. Once on the desired time, hit button A or B to flag that time and loop for more, hit button C to flag the time and return to the menu, and hit button D to return to the menu with no further flagging. As you flag a point, it is changed in color in the editing and secondary area displays and may also be changed in color in the plots of other antennas if those Tsys's are also flagged.. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). Note that, if the display is so crowded that more than one time is plotted at the indicated cursor position (in the horizontal direction only), then a range of times is actually flagged. This option is available in expert mode with abbreviation Time and code letter T (or t). Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- FLAG TIME RANGE This option allows you to flag (delete) Tsys's from a range of times. Move the cursor to the start or end time of the range you wish to flag. The vertical line will follow while the time of the point under the cursor will be displayed in the top left corner of the TV. Hit button A to switch to setting the other end of the time range. Move the cursor to the end point of the desired time range; the second line will follow. Hit button A to switch between the begin and end times; hit button B to flag the Tsys's in the specified range and loop to set another time range; hit button C to flag the Tsys's and return to the menu; or hit button D to return to the menu with no further flagging. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the All vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). This option is available in expert mode with abbreviation Rang and code letter R (or r). Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- FLAG BELOW This option allows you to flag (delete) the Tsys's having value below a cutoff level. Move the cursor to the lowest level you believe in your data. The horizontal line will follow while the value of the point under the cursor will be displayed in the top left corner of the TV. Hit button A or B to flag all Tsys's below the chosen level and loop to do it again, hit button C to flag all Tsys's below the chosen level and return to the menu; or hit button D to return to the menu with no further flagging. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). Note that the flagging is done on the basis of the values of the selected Tsys type (Tsys or Tdif) of each polarization, IF, and baseline individually. This option is available in expert mode with abbreviation Belo and code letter B (or b). Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- FLAG ABOVE This option allows you to flag (delete) the Tsys's having value above a cutoff level. Move the cursor to the highest level you believe in your data. The horizontal line will follow while the value of the point under the cursor will be displayed in the top left corner of the TV. Hit button A or B to flag all Tsys's above the chosen level and loop to do it again, hit button C to flag all Tsys's above the chosen level and return to the menu; or hit button D to return to the menu with no further flagging. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). Note that the flagging is done on the basis of the values of the selected Tsys type (Tsys or Tdif) of each polarization, IF, and baseline individually. This option is available in expert mode with abbreviation Abov and code letter A (or a). Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- FLAG AREA This option allows you to flag (delete) the Tsys's from a range of times and a range of Tsys values. Move the cursor to one corner of the area you wish to flag. The box outline will follow while the time of the data sample nearest the cursor within the box time range and the value corresponding to the cursor vertical position will be displayed in the top left corner of the TV. Hit button A to switch to setting the opposite corner of the area. Hit button A to switch between the opposite corners; hit button B to flag the Tsys's in the specified area and loop to set another area; hit button C to flag the Tsys's and return to the menu; or hit button D to return to the menu with no further flagging. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). Note that the flagging is based solely on the Tsys or Tdif values in the polarization, IF, and baseline displayed in the edit area. When other polarizations, IFs, and baselines are also flagged it is simply the same times as those selected within the box in the edit area. This option is available in expert mode with abbreviation arEa and code letter E (or e). Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- FLAG POINT This option allows you to flag (delete) Tsys's one at a time by moving the cursor to the Tsys and hitting buttons A or B. If you hit button C, the current point is deleted and the program returns to the menu. Button D returns to the menu with no further deletion. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). When other polarizations, IFs, and baselines are also flagged it is simply the same time as that selected by the cursor in the edit area. The cursor needs to be within 5 screen pixels of the Tsys and will take the nearest sample if there is more than one within this radius. This mode is useful for isolated outliers in a crowded display, but is more accurate in complex areas when used within a smaller frame. This option is available in expert mode with abbreviation pOin and code letter O (or o). This command flags only the selected point even if multiple polarizations and/or IFs are displayed. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- FLAG QUICKLY This option allows you to flag (delete) Tsys's one at a time by moving the cursor to the sample (carefully keeping the left mouse button untouched, i.e. up) and then clicking the left mouse button. If you hit buttons A, B, or C, the current point is deleted and the program returns to the menu. Button D returns to the menu with no further deletion. Tsys's for other polarizations, IFs, and antennas may also be flagged depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). When other polarizations, IFs, and baselines are also flagged it is simply the same time as that selected by the cursor in the edit area. The cursor needs to be within 5 screen pixels of the Tsys and will take the nearest sample if there is more than one within this radius. This mode is useful for isolated outliers in a crowded display, but is more accurate in complex areas when used within a smaller frame. This mode is very quick, but requires you to be very careful in your use of the mouse and left mouse button. This option is available in expert mode with abbreviation Quik and code letter Q (or q). This command flags only the selected point even if multiple polarizations and/or IFs are displayed. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- RESTORE TIME This option allows you to un-flag (restore) the Tsys for a specific time. Move the cursor to the time you wish to restore The vertical line will follow while the time of the point nearest the cursor will be displayed in the top left corner of the TV. Hit button A or B to restore the Tsys at that time and loop for more; hit button C to restore the time and return to the menu; or hit button D to return to the menu with no further restoration. Tsys's for other polarizations, IFs, and antennas may also be restored depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). Note that, if the display is so crowded that more than one time is plotted at the indicated cursor position (in the horizontal direction only), then a range of times is actually restored. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- RESTORE AREA This option allows you to un-flag (restore) the Tsys's from a range of times and a range of Tsys values. Move the cursor to one corner of the area you wish to restore. The box outline will follow while the time of the data sample nearest the cursor within the box time range and the value corresponding to the cursor vertical position will be displayed in the top left corner of the TV. Hit button A to switch to setting the opposite corner of the area. Hit button A to switch between the opposite corners; hit button B to restore the Tsys's in the specified area and loop to set another area; hit button C to restore the Tsys's and return to the menu; or hit button D to return to the menu with no further restoration. Tsys's for other polarizations, IFs, and antennas may also be restored depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). Note that the restoration is based solely on the Tsys values in the polarization, IF, and baseline displayed in the edit area. When other polarizations, IFs, and baselines are also restored it is simply the same times as those selected within the box in the edit area. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- SMOOTH TIME RNG This option allows you to smooth (time average) the Tsys's from a range of times. Move the cursor to one end of the time range you wish to smooth. The vertical line will follow while the time of the point under the cursor will be displayed in the top left corner of the TV. Hit button A to switch to setting the other end of the time range. Move the cursor to the end point of the desired time range; the second line will follow. Hit button A to switch between the begin and end times; hit button B to smooth the Tsys's in the specified range and loop to set another time range; hit button C to smooth the Tsys's and return to the menu; or hit button D to return to the menu with no further smoothing. Tsys's for other polarizations, IFs, and antennas may also be smoothed depending on the setting of the All POLARIZ, ALL IF, and ALL ANTENNA flags (shown at the bottom left of the display). Flagged Tsys's may receive "good" values in this process. The Tsys is smoothed even if the Tdif is displayed in the edit area. Furthermore, this operation may only be undone by the REREAD TIME RNG option. See ENTER SMOOTH PS for a description of the smoothing functions available. The basic 2-point smoothing is used solely to replace flagged Tsys's. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- REREAD TIME RNG This option allows you to re-read from the output file the Tsys's from a range of times. Move the cursor to one end of the time range you wish to re-read The vertical line will follow while the time of the point under the cursor will be displayed in the top left corner of the TV. Hit button A to switch to setting the other end of the time range. Move the cursor to the end point of the desired time range; the second line will follow. Hit button A to switch between the begin and end times; hit button B to re-read the Tsys's in the specified range and loop to set another time range; hit button C to re-read the Tsys's and return to the menu; or hit button D to return to the menu with no further re-reading. Tsys's for other polarizations, IFs, and antennas may also be re-read depending on the setting of the ALL vs ONE POLARIZ, ALL vs ONE IF, and ALL vs ONE ANTENNA flags (shown at the bottom left of the display). The Tsys's are read from the output table. Therefore, if only one IF is in memory at a time, these re-read Tsys's may not be the same as in the input table. The display is updated as the Tsys's are read. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- ENTER VALUES This option allows you to select points in the edit window and then type on the terminal (main AIPS window) a new value for the Tsys of that point. A small plus sign appears in the edit window. Move it to a point and then press buttons A, B, or C. The task will prompt you for a new value which will be displayed on the TV if it fits in the current plot. If you hit button C (or D) the process stops, otherwise it continues. Use REPLOT to recompute and display the altered Tdif values. C----------------------------------------------------------------------- ENTER SMOOTH PS This option allows you to type on the terminal (main AIPS window) the type and parameter(s) of the smoothing function. The current type and parameter(s) are displayed at the lower left of the screen. The process of smoothing is based on two windows on the time axis. The cursor is used to set a time-range (t1-t2) to be smoothed. Data from t1-W to t2+W, where W is the smoothing function window, are passed into a smoothing routine and the results used to replace the samples in the t1 through t2 range. The functions are: (1) 2PT Replace Tsys at time t, if flagged, with the linearly interpolated value of the nearest sample above t and below t but within W/2 of t. (2) 2PTH Replace Tsys at time t with the average of the Tsys itself and the linearly interpolated value of the nearest sample above t and below t, but within W/2 of t. (3) BOX Replace Tsys at time t with the average of all Tsys's within W/2 of t. (4) MWF Replace Tsys at time t with the median of all Tsys's within W/2 of t. (5) GAUS Replace Tsys at time t with the weighted average of all Tsys's samples within W/2 of t, using a Gaussian function of abs(time-t) of FWHM of W2. (6) EXP Replace Tsys at time t with the weighted average of all Tsys's samples within W/2 of t, using a Exponential function of abs(time-t) of FWHM of W2. (7) LINE Replace Tsys at time t with the weighted average of all Tsys's samples within W/2 of t, using a linear function of abs(time-t) of FWHM of W2. The ENTER SMOOTH PS asks you 2 or 3 questions: the first to set the type which is case-insensitive but must be left justified, the second to set W in integer seconds, and the third, if needed, to set the full-width at half maximum for the Gaussian and linear weighting functions. The smoothing is done without regard for source. C----------------------------------------------------------------------- ENTER TSYS RNG This option allows you to type on the terminal (main AIPS window) the range of Tsys that will be plotted. It asks you for two numbers, the lower limit and the upper. If the upper limit is > the lower limit, every plot of Tsys will cover this range, leaving out any points outside the range (so be careful). If you type 0 x, where x < 0, then the minimum of each plot will be 0 and the maximum will be self-scaling. Otherwise (e.g. 0 0), each Tsys plot will be self-scaling. The new Tsys range, if selected, is displayed immediately on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. C----------------------------------------------------------------------- ENTER TDIF RNG This option allows you to type on the terminal (main AIPS window) the range of Tdif values that will be plotted. It asks you for two numbers, the lower limit and the upper. If the upper limit is > the lower limit, every plot of phase will cover this range, leaving out any points outside the range (so be careful). Otherwise, each Tdif plot will be self-scaling. The new Tdif range, if selected, is displayed immediately on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tdif's. C----------------------------------------------------------------------- SET SCAN LENGTH This option allows you to change the length in seconds of a "scan" which is the time interval over which the running mean is determined for the Tsys- (aka Tdif) plots and editing. The new Tsys- data, if selected, are displayed immediately on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new data. C----------------------------------------------------------------------- USE EXPERT MODE This option allows you to disable the menu as a form of command input and change to entering one-letter commands from the main AIPS window. The commands must be left-justified and followed by a carriage return and may be in either case. Prompt line(s) appear in the window showing 4-letter abbreviations of the available commands with the one-character code shown in upper case. Enter H or h for a display of the codes and their translation into menu items. Enter X or x to exit the expert mode and return to input via the menu. Note that only some menu items are available in this expert mode and the full help information (such as you are now reading) is not available. C----------------------------------------------------------------------- DO TV LOAD This option will cause the TV display to be updated completely. It is only displayed if you have previously selected the HOLD TV LOAD option. The reason to do this is to delay the screen update while you change more than one of its parameters, i.e., the Tsys's type, display range, antenna to edit, and/or secondary antennas. The status code LOAD PENDING is shown as soon as you have made a change which has not been displayed. When you select the DO TVLOAD option, it is replaced with the HOLD TV LOAD option. C----------------------------------------------------------------------- HOLD TV LOAD This option will cause the TV display to remain unchanged until the DO TV LOAD option is selected. The DO TV LOAD option is displayed if you have previously selected the HOLD TV LOAD option. The reason to do this is to delay the screen update while you change more than one of its parameters, i.e., the Tsys's type, display range, antenna to edit, and/or secondary antennas. When you select this option, it is replaced with the DO TV LOAD option. C----------------------------------------------------------------------- REPLOT This option will redo the full TV plot. It may be of use if the plot has not updated as expected. It is required to get a new computation of Tdif (Tsys / - 1) after editing, smoothing, or restoration operations. C----------------------------------------------------------------------- EXIT This option is used to exit the program. If you have done any flagging or smoothing, the Tsys's will be written back to the output TY table. The output table will remain cataloged as the previous highest version number plus one. C----------------------------------------------------------------------- ABORT This option is used to exit the program. The output TY table will be destroyed. Use this option if you have made no changes to the table, or if you distrust the changes you may have made. C----------------------------------------------------------------------- NEXT POL/IF If there are enough polarizations and IFs in the TY table, this option lets you switch to the "next" correlator. It selects the other polarization (if there are 2) and also selects the next IF if the initial polarization was the highest available. Thus if there are R and L polarizations, it goes from R/1 to L/1 to R/2 to L/2 to ..., eventually circling back to R/1. If CROWDED was true, this option changes the display to a single correlator even if > 1 IF or polarization was plotted when it was selected. The new data are displayed immediately on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new data. This option is available in expert mode with abbreviation Quik and code letter C (or c). C----------------------------------------------------------------------- SWITCH POLARIZ If there are two polarizations in the Tsys table, this option lets you switch between them to select the Tsys's to be displayed and used in editing. If CROWDED was true, then the display of both polarizations at once is also selected by this SWITCH. The Tsys's for the new polarization are displayed immediately on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. C----------------------------------------------------------------------- SWITCH ALL POL This option lets you toggle between having the following flag, smooth, and re-read commands apply to both polarizations and having them apply only to the current polarization. The status lines on the bottom left of the TV screen reflect the current value of this option. C----------------------------------------------------------------------- ENTER IF If you included more than one IF with adverbs BIF and EIF, this option lets you select which one will be displayed and used in editing. If there are more than two IFs or CROWDED was true, you will be prompted to type the number of the desired IF. If CROWDED was true, you may enter 0 to have all IFs displayed at the same time. If there are just two IFs (and CROWDED was false), the program simply switches to the other one. If flags are to be applied to a single IF, they are applied to the IF selected with this option. If all IFs were not read into memory at the start of the job (due to lack of space), then the Tsys's for the current IF are written to the output file (if any flagging or smoothing might have been done) as the Tsys's for the new IF are read in. The Tsys's are immediately displayed on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. C----------------------------------------------------------------------- SWITCH ALL IF This option lets you toggle between having the following flag, smooth, and re-read commands apply to all IFs and having them apply only to the current IF. The status lines on the bottom left of the TV screen reflect the current value of this option. C----------------------------------------------------------------------- SWITCH ALL TIME This option lets you toggle between having the following FLAG ABOVE and FLAG BELOW commands apply to all times and having them apply only to the times displayed in the current edit window (the time range of the frame). C----------------------------------------------------------------------- SWITCH ALL SOURC This option lets you toggle between having the following flag commands apply to all sources and having them apply only to the selected sources. C----------------------------------------------------------------------- SWITCH ALL ANT This option lets you toggle between having the following flag, smooth, and re-read commands apply to all antennas and having them apply only to the current antenna. The status lines on the bottom left of the TV screen reflect the current value of this option. C----------------------------------------------------------------------- ENTER ANTENNA This option allows you to type on the terminal (main AIPS window) the number of the antenna to be used for the main display and for editing. The Tsys's for the new antenna are immediately displayed on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. The Tsys's for this primary antenna are displayed over the current time frame in the editing area and the Tdif's are displlayed in the secondary area. C----------------------------------------------------------------------- ENTER OTHER ANT This option allows you to type on the terminal (main AIPS window) the numbers of ten other antennas to be displayed above the display of the main editing and secondary windows. These comparison displays use the same time frame as the editing window. To display fewer than ten other antennas, enter a 0 for the ones you do not want. You may have no comparison windows if you want to see the largest possible display of the main editing window (enter 10 0's for this option). The Tsys's for the new secondary antennas are immediately displayed on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's C----------------------------------------------------------------------- NEXT ANTENNA This option lets you change to the next antenna in SNEDT's internal list for your primary antenna. The list of other antennas is not changed unless the new antenna occurs there. In that case, the new antenna is removed from the list and a new higher numbered antenna is added at the end of the list. The edit and secondary viewing areas will now contain data from the new primary antenna. The data for the new antennas are immediately displayed on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new data. This option is available in expert mode with abbreviation Nant and code letter N (or n). C----------------------------------------------------------------------- PLOT ALL TIMES This option allows you to select the full time range of the Tsys's as the range to be displayed in all windows. The Tsys's for the new time range are immediately displayed on the TV unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. C----------------------------------------------------------------------- SELECT FRAME This option allows you to select the time range in the Tsys's to be displayed in the editing window using the TV cursor. The Tsys's are first re-displayed using the full time range in the Tsys's (unless the full time range was already displayed). Move the cursor to one end of the desired time range. Hit button A or B to switch to setting the other time limit. Note that you are allowed to make the time range as large or small as you want. Displays that have more than one time plotted in a single horizontal TV pixel are harder to edit accurately but will be quicker than having to do multiple frames when accuracy is less essential. Hit buttons A or B to switch to the other limit, hit buttons C or D to select the frame and return to the menu. The screen is updated immediately, unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. This option is available in expert mode with abbreviation Fram and code letter F (or f). C----------------------------------------------------------------------- NEXT FRAME This option causes the current frame to change to the next higher time range. The "frame" is that time range in the Tsys's available for editing in the edit window. The width of the frame is not changed. The boundaries of the new current frame are shown in the top plot. The screen is updated immediately, unless the HOLD TV LOAD option was selected. In that case, the DO TV LOAD option is displayed and must be selected to see the new Tsys's. C----------------------------------------------------------------------- PREVIOUS FRAME This option causes the current frame to change to the next lower time range. The "frame" is that time range in the Tsys's available for editing in the edit window. The width of the frame is not changed. The boundaries of the new current frame are shown in the top plot. The screen is updated immediately, unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. C----------------------------------------------------------------------- TV ZOOM This option allows you to set the zoom factor and center to blow up the data plot for more accurate cursor positioning. The display is actually shown in zoom only during flagging, un-flagging and re-reading operations (where zoom may help you point more accurately) and during the setting of the zoom. The cursor position controls the zoom center, buttons A and B increment the zoom, button C decrements the zoom, and button D ends the zoom setting and returns to the menu. Instructions appear on the terminal. Note that selecting a small frame is more accurate than simply blowing up a crowded display. C----------------------------------------------------------------------- OFF ZOOM This option resets any zoom factors and zoom center. The display is actually shown in zoom only during flagging, un-flagging and re-reading operations (where zoom may help you point more accurately) and during the setting of the zoom. C----------------------------------------------------------------------- SHOW TSYS This option specifies that Tsys values are to be displayed on the TV and used in the editing. The screen is updated immediately, unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tsys's. This option is available in expert mode with abbreviation Quik and code letter S (or s). C----------------------------------------------------------------------- SHOW TSYS/-1 This option specifies that Tdif values are to be displayed on the TV and used in the editing. The screen is updated immediately, unless the HOLD TV LOAD option was selected. In that case, the status code LOAD PENDING is shown and the DO TV LOAD option is displayed and must be selected to see the new Tdif's. This option is available in expert mode with abbreviation Quik and code letter D (or d). C-----------------------------------------------------------------------