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 Posted: May 25, 2012 - 07:55 PM |
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Joined: Mar 03, 2010
Posts: 535
Location: New Delhi, India
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Hi,
I just want to know how driver can speak to passanger in an Metro train?
Means what technology is used to transfer voice from driver compartment to passenger compartment.
Regards,
Dinesh |
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Posted: May 25, 2012 - 08:24 PM |
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Joined: Jul 18, 2005
Posts: 62240
Location: (using avr-gcc in) Finchingfield, Essex, England
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Posted: May 25, 2012 - 08:38 PM |
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Joined: Oct 30, 2002
Posts: 5719
Location: The Netherlands
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I'd say a PA system is not much more then a microphone connected to a preamplifier followed by a power amplifier and loads of speakers.
There are a few somewhat more advanced systems out there according to this article on Wikipedia. |
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Posted: May 25, 2012 - 08:41 PM |
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Joined: Sep 07, 2004
Posts: 2521
Location: New York State
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| So the driver can talk to passengers by telephone. But how does he know the passenger's phone numbers? Is he allowed to make phone calls while driving? |
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Posted: May 25, 2012 - 08:49 PM |
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Joined: Nov 11, 2003
Posts: 3866
Location: Chicago Illinois USA
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| Duh! He sends them a text! |
_________________
Discursive design,
Torby
Some days, it's just not worth chewing through the restraints.
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Posted: May 25, 2012 - 09:25 PM |
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Joined: Feb 19, 2001
Posts: 25891
Location: Wisconsin USA
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Posted: May 26, 2012 - 07:51 AM |
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Joined: Jan 03, 2006
Posts: 4414
Location: Hemel Hemsptead, UK
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| Especially trained parrots. Five feet high, with lung capacity to match. They walk down the train, with their bright coloured feathers to attract attention, and loudly repeat the message frm the driver in each carriage. |
_________________
Neil Barnes
www.nailed-barnacle.co.uk
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Posted: May 26, 2012 - 08:36 AM |
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Joined: Dec 30, 2004
Posts: 8742
Location: Melbourne,Australia
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Posted: May 26, 2012 - 01:39 PM |
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Joined: Oct 30, 2002
Posts: 5719
Location: The Netherlands
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Posted: May 26, 2012 - 02:49 PM |
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Joined: Jul 18, 2005
Posts: 62240
Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
So the driver can talk to passengers by telephone. But how does he know the passenger's phone numbers? Is he allowed to make phone calls while driving?
Have you seen the original equipment. It was what I think you would describe in this day and age as a "speaker phone". In other words a microphone, a wire and a speaker. That is pretty much what most trains are fitted with.
I guess Dinesh is thinking that a modern system may well be a mic, an ADC, a network transport of some description (perhaps even Ethernet - modern cars have it so why not trains?) and then a DAC and amplifier. This could well be the case but the electronics I was playing with 40+ years ago as a 6-7 year old could just as easily be the solution. |
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Posted: May 26, 2012 - 04:41 PM |
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Joined: Oct 15, 2005
Posts: 530
Location: Russia, Far East Siberia, Irkutsk
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Posted: May 26, 2012 - 04:54 PM |
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Joined: Jun 08, 2011
Posts: 300
Location: Maryland, USA
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clawson wrote:
It was what I think you would describe in this day and age as a "speaker phone". . .
. . .a modern system may well be a mic, an ADC, a network transport of some description (perhaps even Ethernet - modern cars have it so why not trains?) and then a DAC and amplifier. This could well be the case but the electronics I was playing with 40+ years ago as a 6-7 year old could just as easily be the solution.
It makes me wonder about the trains here in Washington, DC. The Metro rail system has seven different rail car designs, from the 1000 series delivered in 1978 to the 7000 series to be delivered next year. Current policy is that 1000 series cars only run in the middle of trains with newer cars at the ends, so each series must interoperate with all of the others. It must be an interesting conversation during the design process to figure out how you ensure that interoperability while taking advantage of new technologies and enabling new features (like the LED station displays in recent cars, and the real-time LCD maps in the upcoming cars), not to mention the major signalling and control systems overhaul that's in the works for this particular system.
(sorry for the thread derail  ) |
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Posted: May 26, 2012 - 06:48 PM |
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Joined: Mar 03, 2010
Posts: 535
Location: New Delhi, India
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Quote:
I guess Dinesh is thinking that a modern system may well be a mic, an ADC, a network transport of some description (perhaps even Ethernet - modern cars have it so why not trains?) and then a DAC and amplifier.
AVR335 we can sample voice. Actually i want to establish communication from room in first floor of my house to room in ground floor but i am not getting how to transfer sampled data to destination DAC controller  |
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Posted: May 26, 2012 - 08:09 PM |
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Joined: Jun 08, 2011
Posts: 300
Location: Maryland, USA
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din.gulu.er wrote:
AVR335 we can sample voice. Actually i want to establish communication from room in first floor of my house to room in ground floor but i am not getting how to transfer sampled data to destination DAC controller
Well, once it's sampled, it's just like any other digital information, isn't it? You could use UART, SPI, ethernet, whatever, as long as the connection can transfer data as rapidly as you're generating it (with room for whatever protocol overhead might be involved). So if you're sampling the audio at, say, 8kHz (human speech phonemes have most of their energy in the 5Hz-4kHz range, according to Wikipedia, but you could probably get away with a lower sample rate at the possible expense of intelligibility) at 8bits, that's a data rate of 64kbps, so could send that via a UART running at 115.2kbaud and have plenty of bandwidth to spare. |
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Posted: May 26, 2012 - 08:58 PM |
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Joined: Oct 30, 2002
Posts: 5719
Location: The Netherlands
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Posted: May 26, 2012 - 09:13 PM |
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Joined: Jul 18, 2005
Posts: 62240
Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
But why the trouble of going the digital route? What's wrong with the good old analogue way?
Exactly - the usual reason for the switch from analogue to digital (think phone or TV systems) is to squeeze more bandwidth out of the same transport mechanism but unless you have 20 flats that might all want to transport voice data over the same copper cable at the same time I'd go with good old fashioned "intercom" using nothing more than a mic. and an amp.
If you want to go for the digital solution then BOTH sides are shown in AVR335. It uses ADC to digitise the speech for storage and it shows the use of timer PWM to act as a "DAC" to convert back from digital to analogue output. Other possibilities on the output side are:
(a) pick an AVR that actually has a DAC
(b) add an external DAC to an AVR
(c) use an R-2R on 8 port pins to form a DAC
Microchip do a nice 12bit that's very easy to interface to an AVR. Most Xmega have DAC built in (but are 3.3V). One or two AT90PWM AVR have DAC as well as ADC. |
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Posted: May 27, 2012 - 08:40 AM |
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Joined: Oct 15, 2005
Posts: 530
Location: Russia, Far East Siberia, Irkutsk
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clawson wrote:
Quote:
But why the trouble of going the digital route? What's wrong with the good old analogue way?
Exactly - the usual reason for the switch from analogue to digital (think phone or TV systems) is to squeeze more bandwidth out of the same transport mechanism but unless you have 20 flats that might all want to transport voice data over the same copper cable at the same time I'd go with good old fashioned "intercom" using nothing more than a mic. and an amp.
If I understand it correctly OP has only two floors 
Really, why does he need digital transport layer? |
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Posted: May 27, 2012 - 07:53 PM |
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Joined: Jan 03, 2006
Posts: 4414
Location: Hemel Hemsptead, UK
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