How does a Sync port work?

Started Sep 26, 2016 | Discussions
OmarAl New Member • Posts: 21
How does a Sync port work?

Hi guys, how are you all doing?

I'm new here and I'm glad to be part of this forum to have discussions on what we love best!

Of course coming here we all ought to have some sort of knowledge about photography in regards to the cameras itself and everything associated with it. However, the one thing I never really completely understood was the Sync port that you would get on some/many cameras and strobes/flashes, wired or wireless.

What I don't understand of it is, how does it work exactly? Does the camera from the port (or even from the hot-shoe when adapter is used) send a specific signal to the light source to ignite? Does it merely act like a on/off switch?? Or just an electrical signal that would trigger for a light to go off??? I wouldn't know if this is actually a simple or complex case of how this works.

I hope you understand what I'm trying to describe, if not please do let me know and I'll try to further clarify my question. I do apologize if this may be a bit much for a new comer here.

Thanks all and I sincerely look forward hearing back from you all!

markkuk Contributing Member • Posts: 727
Re: How does a Sync port work?

It's a simple on/off switch. It's normally open and the circuit closes when the flash should be fired.

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Klaus dk
Klaus dk Veteran Member • Posts: 6,115
Re: How does a Sync port work?
1

markkuk wrote:

It's a simple on/off switch. It's normally open and the circuit closes when the flash should be fired.

True, except that in modern cameras, it is an electronic switch. If you use an old flash with a trigger voltage > 5V, your camera will protect itself and not fire the flash, or the flash might fry the electronics of your camera.

Modern speedlights and other equipment is quite safe to use.

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OP OmarAl New Member • Posts: 21
Re: How does a Sync port work?

Hi guys, thanks so much for reply here!

That's really interesting, if you're saying it's technically a on/off switch, how long does this switching last for? cause it just seems a bit too quick for it to flick on and off, hehehe.

Also how is this signal generated? Can it be replicated?? And is it the same across all (modern) cameras???

Klaus dk
Klaus dk Veteran Member • Posts: 6,115
Re: How does a Sync port work?

Google and wikipedia are your friends.

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OP OmarAl New Member • Posts: 21
Re: How does a Sync port work?

Ohhh I've tried that sooo many times, I just simply couldn't get an answer, thus why I resorted and came here, also the reason why I registered.

chuxter Forum Pro • Posts: 21,714
Re: How does a Sync port work?

OmarAl wrote:

Hi guys, how are you all doing?

I'm new here and I'm glad to be part of this forum to have discussions on what we love best!

Of course coming here we all ought to have some sort of knowledge about photography in regards to the cameras itself and everything associated with it. However, the one thing I never really completely understood was the Sync port that you would get on some/many cameras and strobes/flashes, wired or wireless.

What I don't understand of it is, how does it work exactly? Does the camera from the port (or even from the hot-shoe when adapter is used) send a specific signal to the light source to ignite? Does it merely act like a on/off switch?? Or just an electrical signal that would trigger for a light to go off??? I wouldn't know if this is actually a simple or complex case of how this works.

I hope you understand what I'm trying to describe, if not please do let me know and I'll try to further clarify my question. I do apologize if this may be a bit much for a new comer here.

Thanks all and I sincerely look forward hearing back from you all!

We understand very well. BUT, modern photographers don't use the sync port. I must have a dozen cables that connect to that socket, which is called a "PC Sync" socket.

In old mechanical cameras, there was simply a mechanical switch that closed at the correct time. "X-sync" was common, but there were other timings too.

I have no clue what the "pulse width" of the signal from a "PC Sync" socket is. It probably doesn't matter much, as the flashes are edge triggered.

If you have a camera and a scope, look at the signal. You may have to add a small pull-up resistance?

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Klaus dk
Klaus dk Veteran Member • Posts: 6,115
Re: How does a Sync port work?

OmarAl wrote:

Ohhh I've tried that sooo many times, I just simply couldn't get an answer, thus why I resorted and came here, also the reason why I registered.

OK, I did it for you. Just click on the link I provided in my previous post.

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kli
kli Veteran Member • Posts: 3,360
Re: How does a Sync port work?

OmarAl wrote:

...Also how is this signal generated? Can it be replicated?? And is it the same across all (modern) cameras???

It's a simple short from sync to ground.  And yeah, it's pretty much the same, if the flash/camera follows the ISO standard for hotshoes and flash feet. Voltage, however, can vary.

On a PC connector, the inner pin is sync, the ring outside is ground.  But nearly any connector that can communicate those two signals and a short between them can be used. That's why a variety of connectors can be used for sync: household plugs, 3.5mm minijack, PC, 2.5 minijack, or whatever.  With the minijacks, the tip is sync, base is ground.  On the flash foot, the pin in the center of the "square" is sync, the rail contacts on the side above  is ground. On the hotshoe on the camera, the contact in the middle is sync, and the rails are ground.

If you simply take a wire and short the center pin to the side rail contact, (and the flash is on) the flash will fire.

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OP OmarAl New Member • Posts: 21
Re: How does a Sync port work?

Klaus dk wrote:

Google and wikipedia are your friends.

Ahhh yes, I can see it now, sorry about that, but yes I've actually read that wiki page before!

chuxter wrote:

We understand very well. BUT, modern photographers don't use the sync port. I must have a dozen cables that connect to that socket, which is called a "PC Sync" socket.

In old mechanical cameras, there was simply a mechanical switch that closed at the correct time. "X-sync" was common, but there were other timings too.

I have no clue what the "pulse width" of the signal from a "PC Sync" socket is. It probably doesn't matter much, as the flashes are edge triggered.

If you have a camera and a scope, look at the signal. You may have to add a small pull-up resistance?

Edge Triggered! That is probably what I was after! I don't own or even have access to a oscilloscope unfortunately (I wouldn't know where to begin if I were to use one either!), but if I am thinking correctly, everytime the flash device receives a "positive edge" from the signal that is when it triggers the bulb to flash for "x" amount of time? Thus the longer the positive edge is the longer the light remains illuminated??

kli wrote:

On a PC connector, the inner pin is sync, the ring outside is ground. But nearly any connector that can communicate those two signals and a short between them can be used. That's why a variety of connectors can be used for sync: household plugs, 3.5mm minijack, PC, 2.5 minijack, or whatever. With the minijacks, the tip is sync, base is ground. On the flash foot, the pin in the center of the "square" is sync, the rail contacts on the side above is ground. On the hotshoe on the camera, the contact in the middle is sync, and the rails are ground.

If you simply take a wire and short the center pin to the side rail contact, (and the flash is on) the flash will fire.

Yes, this was something I was going to mention at the very least, I have seen 3.5mm cables being used for such operation (and probably even prefered over the Sync cord), this is super handy for me since I am a videographer/filmmaker so 3.5mm cables are common to me, hehehe.

Another thing as well was the hotshoe. Does this work exactly the same way as a Sync socket does except the signal is at the top of the camera and one would need an adapter to tap into using the center pin??

markkuk Contributing Member • Posts: 727
Re: How does a Sync port work?

OmarAl wrote:

 but if I am thinking correctly, everytime the flash device receives a "positive edge" from the signal that is when it triggers the bulb to flash for "x" amount of time? Thus the longer the positive edge is the longer the light remains illuminated??

No. When the camera connects the two conductors of the sync port or hotshoe together the flash fires. The duration of the light is determined by the flash, not the camera.

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chuxter Forum Pro • Posts: 21,714
Re: How does a Sync port work?

OmarAl wrote:

Edge Triggered! That is probably what I was after! I don't own or even have access to a oscilloscope unfortunately (I wouldn't know where to begin if I were to use one either!), but if I am thinking correctly, everytime the flash device receives a "positive edge" from the signal that is when it triggers the bulb to flash for "x" amount of time? Thus the longer the positive edge is the longer the light remains illuminated??

No.

First as someone else mentioned, the switch [either mechanical or electronic] pulls the center contact to ground. Thus, the leading edge is negative going. As I mentioned to see this, you will have to pull the line up w/ a resistance [about 5000 Ohms?] going to something like 3-10 volts.

The fall time of the leading edge is VERY short, especially w/ mechanical contacts. Even w/ an electronic switch [transistor], the fall time is probably less than a micro-second. The fall time has absolutely nothing to do w/ the duration of the flash pulse! The pulse just initiates the flash. The duration of the flash pulse is a different and lengthy discussion.

kli wrote:

On a PC connector, the inner pin is sync, the ring outside is ground. But nearly any connector that can communicate those two signals and a short between them can be used. That's why a variety of connectors can be used for sync: household plugs, 3.5mm minijack, PC, 2.5 minijack, or whatever. With the minijacks, the tip is sync, base is ground. On the flash foot, the pin in the center of the "square" is sync, the rail contacts on the side above is ground. On the hotshoe on the camera, the contact in the middle is sync, and the rails are ground.

If you simply take a wire and short the center pin to the side rail contact, (and the flash is on) the flash will fire.

Yes, this was something I was going to mention at the very least, I have seen 3.5mm cables being used for such operation (and probably even prefered over the Sync cord), this is super handy for me since I am a videographer/filmmaker so 3.5mm cables are common to me, hehehe.

Another thing as well was the hotshoe. Does this work exactly the same way as a Sync socket does except the signal is at the top of the camera and one would need an adapter to tap into using the center pin??

Yes. The center pin is generally identical to the center pin of the PC socket. There are MANY adapters on the market.

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Ragnar Jensen
Ragnar Jensen Regular Member • Posts: 402
Re: How does a Sync port work?
1

chuxter wrote:

OmarAl wrote:

Edge Triggered! That is probably what I was after! I don't own or even have access to a oscilloscope unfortunately (I wouldn't know where to begin if I were to use one either!), but if I am thinking correctly, everytime the flash device receives a "positive edge" from the signal that is when it triggers the bulb to flash for "x" amount of time? Thus the longer the positive edge is the longer the light remains illuminated??

No.

First as someone else mentioned, the switch [either mechanical or electronic] pulls the center contact to ground. Thus, the leading edge is negative going. As I mentioned to see this, you will have to pull the line up w/ a resistance [about 5000 Ohms?] going to something like 3-10 volts.

The fall time of the leading edge is VERY short, especially w/ mechanical contacts. Even w/ an electronic switch [transistor], the fall time is probably less than a micro-second.

Good guess. There is an international standard for flash triggers. ISO 10330 "Photography — Synchronizers, ignition circuits and connectors for cameras and photoflash units — Electrical characteristics and test methods."

It states that for an electronic switch it should pull the flash's trigger voltage down to 1.5V or lower in less than a microsecond and then keep it there for at least ten microseconds. The standard recommends that the camera holds the trigger voltage at 1.5V or lower until the shutter starts to close, though.

The standard for mechanical switches is a bit more complex, since it allows for contact bounce and chatter, but the gist of it is the same; pull down to 1.5V or lower for at least ten microseconds.

The fall time has absolutely nothing to do w/ the duration of the flash pulse! The pulse just initiates the flash. The duration of the flash pulse is a different and lengthy discussion.

kli wrote:

On a PC connector, the inner pin is sync, the ring outside is ground. But nearly any connector that can communicate those two signals and a short between them can be used. That's why a variety of connectors can be used for sync: household plugs, 3.5mm minijack, PC, 2.5 minijack, or whatever. With the minijacks, the tip is sync, base is ground. On the flash foot, the pin in the center of the "square" is sync, the rail contacts on the side above is ground. On the hotshoe on the camera, the contact in the middle is sync, and the rails are ground.

If you simply take a wire and short the center pin to the side rail contact, (and the flash is on) the flash will fire.

Yes, this was something I was going to mention at the very least, I have seen 3.5mm cables being used for such operation (and probably even prefered over the Sync cord), this is super handy for me since I am a videographer/filmmaker so 3.5mm cables are common to me, hehehe.

Another thing as well was the hotshoe. Does this work exactly the same way as a Sync socket does except the signal is at the top of the camera and one would need an adapter to tap into using the center pin??

Yes. The center pin is generally identical to the center pin of the PC socket. There are MANY adapters on the market.

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Ragnar

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OP OmarAl New Member • Posts: 21
Re: How does a Sync port work?

Good morning gentlemen,

I do apologise for my late reply! Things at home gotten in the way a bit thus slightly forgetting and making it hard to come back and get back to you wonderful people, I hope you understand!

markkuk wrote:

No. When the camera connects the two conductors of the sync port or hot shoe together the flash fires. The duration of the light is determined by the flash, not the camera.

Ahhh I see, I always thought it was the camera, especially since it goes so fast! I understand that the flash would have different intensities of light power but always at the same duration. If that's the case then, how does a flash device determine how long the light should last for? Does the light bulb itself play an important part to this??

chuxter wrote:

No.

First as someone else mentioned, the switch [either mechanical or electronic] pulls the center contact to ground. Thus, the leading edge is negative going. As I mentioned to see this, you will have to pull the line up w/ a resistance [about 5000 Ohms?] going to something like 3-10 volts.

The fall time of the leading edge is VERY short, especially w/ mechanical contacts. Even w/ an electronic switch [transistor], the fall time is probably less than a micro-second. The fall time has absolutely nothing to do w/ the duration of the flash pulse! The pulse just initiates the flash. The duration of the flash pulse is a different and lengthy discussion.

...

chuxter wrote:

Yes. The center pin is generally identical to the center pin of the PC socket. There are MANY adapters on the market.

Wow, that was a bit for me to take in and trying hard to understand it too but highly appreciative for you mentioning this! As I have gathered, it is the flash device that determines the duration of the emitted light and not the camera and it all signals (either from mechanical or electronic) from the Ground contact of the hot shoe, thus if I am correct it is like across ALL cameras I suppose??

Rajraj wrote:

Good guess. There is an international standard for flash triggers. ISO 10330 "Photography — Synchronizers, ignition circuits and connectors for cameras and photoflash units — Electrical characteristics and test methods."

It states that for an electronic switch it should pull the flash's trigger voltage down to 1.5V or lower in less than a microsecond and then keep it there for at least ten microseconds. The standard recommends that the camera holds the trigger voltage at 1.5V or lower until the shutter starts to close, though.

The standard for mechanical switches is a bit more complex, since it allows for contact bounce and chatter, but the gist of it is the same; pull down to 1.5V or lower for at least ten microseconds.

That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it

Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??
For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?

Leonard Migliore
Leonard Migliore Forum Pro • Posts: 17,442
Maybe not the best idea
1

OmarAl wrote:

That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it

Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??
For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?

Note that electronic flash units use high voltage to fire the flashtube. It can be quite dangerous to disassemble a flash unit and then power it up to try to fire it, especially if you're poking around it at random.

http://www.sciforums.com/threads/shock-from-a-camera-flash-is-lethal.40865/

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Leonard Migliore

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Ragnar Jensen
Ragnar Jensen Regular Member • Posts: 402
Re: Maybe not the best idea
1

Leonard Migliore wrote:

OmarAl wrote:

That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it

Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??

A couple of small capacitors, an electronic switch of some kind (a Triac or SCR) and a transformer are the main components of the trigger circuit.

For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?

Don't do that. You will probably hurt the flash or yourself. You could possibly kill yourself.

Note that electronic flash units use high voltage to fire the flashtube. It can be quite dangerous to disassemble a flash unit and then power it up to try to fire it, especially if you're poking around it at random.

http://www.sciforums.com/threads/shock-from-a-camera-flash-is-lethal.40865/

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Leonard Migliore

Sage advice from Leonard. There is a large capacitor in there that can store a LOT of energy. It is typically charged to 300-350 Volts. The transformer in the trigger circuit carries a couple of hundred Volts on its primary side and several thousands on the secondary side when it makes the flash go off. You really need to know what you're doing if you take a flash apart.

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Ragnar

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OP OmarAl New Member • Posts: 21
Re: Maybe not the best idea

Leonard Migliore wrote:

OmarAl wrote:

That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it

Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??
For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?

Note that electronic flash units use high voltage to fire the flashtube. It can be quite dangerous to disassemble a flash unit and then power it up to try to fire it, especially if you're poking around it at random.

http://www.sciforums.com/threads/shock-from-a-camera-flash-is-lethal.40865/

Heey guys, sorry once again for the late reply, I didn't get to see your replies when you've made them before I went to A&E with some minor burns on my fingers when handling my friend's 430EX Speedlite when poking around whilst seeing if I can repair it, really regret not coming back here sooner when you guys mentioned the amount of voltage a cap can contain which really surprised me after...

...JOKING!!!

I am very aware of the hazard if one does commit such an act and would never attempt it lightheartedly! I also don't intend to do so either as I merely (for now) just want to understand how this all works, everything being said so far has really been helpful and I'm sure it would be beneficial for others too.

Therefore I was wondering, I came across an article showing you how to build a flash with an optical slave:

http://www.diyphotography.net/how-to-build-a-flash-with-an-optical-slave/

Check it out, it's very interesting stuff, very similar to a disposable camera circuit, no?

Anyway this got me thinking, since the signal for the triggering the flash comes from the ground pin (or the circuit?), could this signal be used to trigger flash from such a build if it was hooked in the right places perhaps??

OP OmarAl New Member • Posts: 21
Re: How does a Sync port work?

Anyone at all may I ask?

Klaus dk
Klaus dk Veteran Member • Posts: 6,115
Re: Maybe not the best idea

OmarAl wrote:

Leonard Migliore wrote:

OmarAl wrote:

That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it

Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??
For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?

Note that electronic flash units use high voltage to fire the flashtube. It can be quite dangerous to disassemble a flash unit and then power it up to try to fire it, especially if you're poking around it at random.

http://www.sciforums.com/threads/shock-from-a-camera-flash-is-lethal.40865/

Heey guys, sorry once again for the late reply, I didn't get to see your replies when you've made them before I went to A&E with some minor burns on my fingers when handling my friend's 430EX Speedlite when poking around whilst seeing if I can repair it, really regret not coming back here sooner when you guys mentioned the amount of voltage a cap can contain which really surprised me after...

...JOKING!!!

I am very aware of the hazard if one does commit such an act and would never attempt it lightheartedly! I also don't intend to do so either as I merely (for now) just want to understand how this all works, everything being said so far has really been helpful and I'm sure it would be beneficial for others too.

Therefore I was wondering, I came across an article showing you how to build a flash with an optical slave:

http://www.diyphotography.net/how-to-build-a-flash-with-an-optical-slave/

Check it out, it's very interesting stuff, very similar to a disposable camera circuit, no?

Anyway this got me thinking, since the signal for the triggering the flash comes from the ground pin (or the circuit?), could this signal be used to trigger flash from such a build if it was hooked in the right places perhaps??

I may have misunderstood your question, but the "signal" is not coming from the ground pin, it is the short from the flash circuit to ground that triggers the flash. It can be implemented with a simple morse key or doorbell pushbutton, or any circuit that will allow the necessary current through.

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iancrowe Senior Member • Posts: 1,477
Re: Maybe not the best idea

OmarAl wrote:

Leonard Migliore wrote:

OmarAl wrote:

That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it

Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??
For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?

Note that electronic flash units use high voltage to fire the flashtube. It can be quite dangerous to disassemble a flash unit and then power it up to try to fire it, especially if you're poking around it at random.

http://www.sciforums.com/threads/shock-from-a-camera-flash-is-lethal.40865/

Heey guys, sorry once again for the late reply, I didn't get to see your replies when you've made them before I went to A&E with some minor burns on my fingers when handling my friend's 430EX Speedlite when poking around whilst seeing if I can repair it, really regret not coming back here sooner when you guys mentioned the amount of voltage a cap can contain which really surprised me after...

...JOKING!!!

I am very aware of the hazard if one does commit such an act and would never attempt it lightheartedly! I also don't intend to do so either as I merely (for now) just want to understand how this all works, everything being said so far has really been helpful and I'm sure it would be beneficial for others too.

Therefore I was wondering, I came across an article showing you how to build a flash with an optical slave:

http://www.diyphotography.net/how-to-build-a-flash-with-an-optical-slave/

Check it out, it's very interesting stuff, very similar to a disposable camera circuit, no?

Anyway this got me thinking, since the signal for the triggering the flash comes from the ground pin (or the circuit?), could this signal be used to trigger flash from such a build if it was hooked in the right places perhaps??

I can't help thinking that you would find is easier, safer and possibly cheaper to invest in something like the Yongnuo YN-560 Mk. IV flash.

The YN-560 comes with a built in PC sync socket, optical triggering (capable of ignoring pre-flash), variable power output, a zoomable tilt swivel head and built in radio transmitter and receiver for wireless remote triggering. All for about the cost of the components and casing required for the above circuit.

Ian

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