Film-Tech Forum ARCHIVE: Questionable Change-over logic

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Posted by Frank Angel (Member # 248) on 02-25-2003, 02:12 AM:

At the moment I am modifying (in my head) an installation which for some unknown reason has two change-over switches (momentary push-buttons) on each projector console -- the main change-over switch which is what you'd expect: it opens the c/o shutter on its local machine and closes the c/o shutter on the outgoing machine and switches the CP55 preamps. Fine. But the second switch does just the opposite, for which I cannot find any logic for such a function. Why would anyone want to switch sound and picture to the other machine if you are not standing at it? It is useless.

On occasion the operator would miss a motor cue and have to go to black. He instinctively pushes the "reverse" button. Well, yes, it does shutter his machine, but it also opens the shutter of the outgoing reel on the other projector; either way he's screwed. So I want to change that switch to a complete KILL function. Hitting it will close the local machine's c/o shutter but not open the second machine's.

But here's the question. I also want that switch put the CP55 in its MUTE state -- in other words, this will be an emergency or "Panic" switch, when the best thing would be for everything to stop in the theatre.

But here's the dilemma -- it would be very easy to have a contact on the switch activate the MUTE function. BUT, the question is, will pushing the main change-over switch, which normally toggles the projector selector in the CP55 (Prjt 1 or Prjt 2), will that automatically defeat the MUTE and resume sound from whichever projector's c/o switch was activated? OR, do I need an additional contact to actually unMUTE the processor AND then activate the projector sound?

I will have another set of contacts on that switch if it is necessary because I am also divorcing the shutter c/o from the console switch and leaving only the audio c/o on it. In a rep house we need to be able to lag the sound change-over after the picture in order to catch those last 20 frames of sound which many times has been crucial. If picture and sound change-over are simultanious and married on one switch, you can't do that lag. I'm actually dragging out the ole tried and true foot switches for the picture c/o.

Anyone know off-hand if the CP55 logic needs two contacts -- 1)to unmute a muted state AND then an extra pulse to activate whichever preamp? OR (and this is what I hope) will the mute state unmute by virtue of either projector being called?

Sorry guys, I know this sounds rather rudimentary, but I am drawing this on a napkin in my jammies and I don't have a CP55 manual here.

Frank

Posted by Brad Miller (Member # 2) on 02-25-2003, 02:16 AM:

If I remember correctly, the one mute control will mute and unmute back and forth every time you hit it. Also, I do believe if you pulse the desired softkey it will force itself out of mute. So ideally you need to take your master sound changeover button and wire it through a 4 position selector switch so you can tell it that once you initiate the changeover to select a certain format. That way you don't have to worry about whether the mute is on or off from your "panic" button.

Posted by Daryl C. W. O'Shea (Member # 1303) on 02-25-2003, 02:45 AM:

Brad's right about the mute button. Pulsing the same contact will turn it on or off. Select any format (even the current one) will un-mute the processor.

Now if I remember correctly (and if you're lucky), selecting another projector will also un-mute the processor, but I could be mistaken.

If it doesn't the easiest place to wire a four position switch would be right at the processor. If you want to be able to switch from 1->2 and 2->1 using the 'panic' button you'll need two 4 position switches (or a single DP4T) and some diodes.

Posted by Carl Martin (Member # 1146) on 02-25-2003, 06:14 AM:

i've never run c/o but it seems like the setup as it exists could be useful if, say, a print comes in without existing cue marks. rather than scribing cues or otherwise marking the image area, little flags could be put on the edge of the film. if you stand at the projector whose reel is ending, you can then changeover to the other projector when you see the flag enter the filmhead, or hear it go through the gate, depending on its placement. you'd probably also want motor switches for both projectors in each position. even if the print has cues, i would think this method might make for more frame-perfect changeovers.

carl

Posted by Joe Beres (Member # 678) on 02-25-2003, 10:11 AM:

Frank,
I wouldn't call your system useless. It is really helpful in certain applications. I have a similar set-up here, and it comes in handy in two situations. It really helps when you are aligning two images and setting focus. Being able to switch back and forth quickly and A/B makes for fast work.
Also, I periodically run shows, similar to Inside the Actor's Studio, in which I run short, mid-reel clips. I can put easily seen cues on the edge of the film, and start and stop them without shuffling over to the other projector. It's a convenience that helps me run a high-profile, high-stress event more smoothly. It isn't a necessity, but it is really nice.

Posted by Christopher Seo (Member # 7) on 02-25-2003, 11:14 AM:

There is some merit to having a "reverse" changeover switch at each projector, which is the case at the theatre I work, but I still agree with Frank that an all-close, all-mute switch is also much needed.

For example, while the last reel of a show was playing I have threaded up a reel of the next (i.e., different) show on the other projector and started running it through, intending to do a quick focus/framing check during intermission. Well, since the only way I can end the current show is to change pix and sound over to the other machine, I must resort to pulling the exciter lamp so my test reel doesn't end up blasting into the auditorium.

As Frank said, an all-close, all-mute button would also be handy in case of a missed changeover... [Embarrassed]

Posted by Scott Norwood (Member # 30) on 02-25-2003, 02:08 PM:

Frank--I _like_ having the ability to changeover from either machine while standing next to either machine. It's useful when threading (to select the other machine without having to walk around) and in case one accidentally hits the c/o button too soon. The "all close" idea is interesting, but it doesn't seem nearly as useful and it seems like it would confuse a projectionist who isn't familiar with the venue. Do you really have that many problems with missed changeovers? If it happens more than once a year or so, then you probably have bigger issues.... In any case, please leave a big note in the booth explaining how the "all close" system works. Some relief operator will thank you for it.

Posted by Steve Kraus (Member # 476) on 02-25-2003, 03:47 PM:

Strong's VIP-based studio projection system has "anti" changeover buttons, too. They come in handy in some instances but I never found it useful enough to install similar buttons in my own facility. One use is simply to kill the show at the very end, something normally done by switching to the non operating machine. However, using this technique to kill something still running doesn't really work with Dolby Digital because the digital source won't switch to the non running machine (at least that was the logic on the CP500D. So an actual kill (all close, all mute) button might be useful. But undoing the mute by pulsing the format button will cause a tiny disruption in sound if done on this CP so you wouldn't want such pulsing to be done on each C/O whether needed or not. But the analog processors may not have the same problem.

Posted by John Hawkinson (Member # 1135) on 02-25-2003, 08:38 PM:

I'm sure this doesn't help Frank (because has has no automation controller), but in our setup, the changeover button acts as a kill switch if its pressed a second time. This is a handy bit of overloading.

We also have a 10-button control panel near each projector (as well as in other parts of the booth) that lets you access all the automation functions, including changeovers, sound format selection, digital override, volume changes, voice-of-god, kill switch, etc.

--jhawk

Posted by Steve Kraus (Member # 476) on 02-25-2003, 09:27 PM:

in our setup, the changeover button acts as a kill switch if its pressed a second time. This is a handy bit of overloading.

I don't like that idea as an inadvertent bounce would kill the show not to mention that if one ever suddenly has a changeover sticking (particularly the closing one that you're not near) you would not be able to give it an extra zap and a split second glitch turns into the several seconds it takes to get to the other machine.

Posted by Daryl C. W. O'Shea (Member # 1303) on 02-25-2003, 09:34 PM:

All this brings up why I prefer seperate sound and picture changeover controls (especially c/o controls that you can mute). In the rare event that you muck up the changeover you can mute the sound and do a picture changeover to the incoming machine without opening (or quickly closing if already open) the hand douser on the incoming machine. When the picture finally hits the gate on the incoming machine you open the douser and complete the sound changeover. No stopping the show, no showing the outgoing tail, and no loud noise in the auditorium.

Posted by Frank Angel (Member # 248) on 02-25-2003, 11:47 PM:

Damn, I love this forum.

All good points. You're right, the need for a kill switch doesn't happen very often, but still, when it does, I really wish the kid had an easy way of lessening its impact in the house. Without it, you wind up with a real mess in the house (ever hear what a tail running out sounds like with four 4000w subbass Community bins in your system?....it ain't a pretty sound!)

And you're right Joe, I didn't remember the convenience being able to switch back and forth between two machines when aligning light output and uniformity.

I think the final design will be to keep the back and forth ability but add an ALL KILL button too. And, of course, there was no question about separating sound and picture c/o switches....any of you guys ever use the foot peddel switches? --you really get to put your whole body into the change-over!

Thanks guys.

Frank

Posted by Daryl C. W. O'Shea (Member # 1303) on 02-25-2003, 11:55 PM:

quote:
any of you guys ever use the foot peddel switches? --you really get to put your whole body into the change-over!

Yup -- at a couple drive-ins. Some with sound changeover on the floor too. Foot switches just make it too easy, you don't even have to get out of your chair to do the changeover. [Smile]

Posted by John Anastasio (Member # 607) on 02-26-2003, 02:30 AM:

I remember the foot pedal switches. It was neat stomping on those things. I haven't seen them in decades.

Posted by Scott Norwood (Member # 30) on 02-26-2003, 08:43 AM:

Steve--is that the setup with the jumbo-size red and green buttons on the projector base? If so, then I didn't realize that it was a standard configuration from Strong...I had assumed that it was something clever that the installation company had done.

Kinoton FP30s (and maybe other models) have two changeover buttons that serve the same purpose, too, though they are annoyingly located on the front of the machine.

I like having footpedals for picture and pushbuttons for sound (probably because that's the arrangement that I started with), but that setup seems to be uncommon in newer installations. What I can't stand is when someone has decided to mount switches or pushbuttons which don't control projector motor or changeover on the wall or projector base near the actual projector controls. The Cape Cinema (see pic gallery) has the "curtain" pushbutton located next to the "changeover" pushbutton. Guess who hit the wrong button one night....

Posted by Stephen Furley (Member # 1277) on 02-26-2003, 09:06 AM:

Early Kinotons had a sort of crescent-shaped rocker arrangement, near the sound head; flick it one way to start, the other way to stop, and push it in for changeover. Later models had push buttons in a similar position.

A pair of new FP-30Ds which I ran last year has five buttons, motor start and stop, inch, changeover and one which closes that machine, without opening the other, but they are on the front of the machine, not the operating side, but behind, and underneath the lens. These machines were positioned very close to the front wall of the box, so they are difficult to get at, my arms aren't long enough to reach them while looking through the viewing port, so I have to bend down low enough to look through the projection port, and then tend to get the light reflected in my eyes. Why they put the controls there, I don't know.

Posted by Steve Kraus (Member # 476) on 02-26-2003, 09:06 AM:

Yes, Scott.

IMHO the forward / reverse unit left a lot to be desired. (Not that there is ever much call for reverse.) The lower spindles utilized Moviola-like clutches so that two were driven going forward, the other one on reverse and these were problematic. Nothing like having the takeup peter out near the end of 2000' reels. And the 5-Star modified with a mag head is no match for the venerable Century R-8 (former 3-D Mag "dummy" placed under a projector head modified for by-pass) with its full Davis-Loop twin flywheels. The units shown are no longer used for interlock projection the facility having acquired a pair of dubbers.

Back to the subject of controls, having them all the way at the back of the console is, to me, very awkward, although there is no reason they can't be paralleled with some on the front wall.

Posted by Scott Norwood (Member # 30) on 12-01-2003, 07:09 PM:

[digging up old threads]

Frank--what did you end up doing?

BTW, I just tried it this weekend and the CP650 stays in mute mode even when the sound changeover is switched from one projector to another. Switching to a different format will un-mute it, however. Not that this matters for your place, but maybe someone else will find it useful.

Posted by Gary Crawford (Member # 2038) on 12-03-2003, 11:16 AM:

I found an unplanned way to install an audio mute. We use foot pedals and toggle switches, just like the old days. One sound toggle switch went bad so I replaced it. I couldn't find a switch anywhere that was a DPDT WITHOUT an "off" in the center position. So I installed the new one with the center off and I realized I had a mute! Click it to the middle. I replaced the other switch as well as I liked the ability to mute from both sides.

My X-over pedals will trip if you sneeze on them, they are so sensitive. Others I've had in other houses were so stiff you almost had to jump on them.

Once I had the X-over shutter on the #2 (right hand) machine fry and was useless. In the meantime I stood between the machines for all X-overs. I could reach the other motor switch just fine across the front of the machine, then manually, by hand, flipped both X-over shutters, then quickly threw the audio switch. Looked fine onscreen, no one noticed.

Posted by Frank Angel (Member # 248) on 12-04-2003, 02:07 AM:

Scott, what I actually did was.....procrastinate. So far I've done nothing yet except buy the additional switches and then go to the World 3D Festival on the other coast. Then came back and had to do lots of prep for a special screening of 2001 with guest Keir Dullea. And still haven't dug myself out of the pile of work on my desk.

But after taking all the good advice here under advisment, whenever I finally do get around to messing with it, this is the way it is going to play out:

1) The existing CHANGE-OVER switch will remain as-is, a standard momentary pulsing of the change-over shutters (one open, the other close) on both projectors.

2) There will be a second switch (existing momentary) that will be converted from what it is now -- a "reverse change-over" -- to an "KILL ALL" switch. As such, it will close both shutters and mute audio. I still don't know if the CP55 will require nothing more than the momentary pulses from the CHANGE-OVER switches and the KILL ALL switches or if I will have to add a latching relay to hold it open or closed, whatever, it will be very simple.

And 3) Because of the good advice from you and Joe B, I am adding a small toggle out of easy access at the bottom of the projector switch panel which will have a TEST and a NORMAL mode; it will also have a green LED indication for the normal mode and an anoying blinking red LED indication when it is in the TEST mode. In the NORMAL mode, the KILL ALL switch will be just that, but in the TEST mode, the KILL ALL switch will revert to its original "reverse change-over" function. As you both pointed out, there are legitimate situations where the ability to switch back and forth between both projectors from one location can be helpful. But those are the exception, so I give the projectionist the ability to purposely change the function when he needs that.

Now all I have to do is get my butt in gear and do it.

Posted by Steve Kraus (Member # 476) on 12-04-2003, 08:51 PM:

Leaving aside the matter of toggles and blinking LED's, the KILL ALL button is easily implemented. The traditional C/O wiring has two circuits, both with a SPST button wired to open near and close far. To have a kill all button first we need to separate the wiring so that close is not tied permanently to the open of the opposite machine. This is most simply done by replacing the SPST C/O buttons with DPST. Power is still fed to both poles but the open and closes are wired to separate contacts so that they are kept separate. Then the KILL ALL buttons are added to both machines. If it were only necessary to close the C/O's it could be done with DPST buttons (power common to both poles, the output contacts wired separately to each C/O close coil). But a third pole would be needed to do the mute on each so simpler to use SPST buttons (maybe the old C/O buttons) in parallel hooked to the coil of a 3PST relay (probably implemented with a 4PDT but 3PST is all that is used). Two poles wired to power and to the two close coils and the other contact wired to the CP's mute feature.

A reverse (or anti as I like to call it) C/O button would be simple to wire as a completely separate thing just a parallel duplication of the C/O button from the opposite machine.