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Conference nesbit::modular

Title:	Embedded and Real Time Modular Computing Conference

Moderator:	IRNBRU::GRANT

Created:	Tue Sep 05 1995
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	235
Total number of notes:	1091

223.0. "Telephony type power supply?" by MQOOA::LEDOUX (Vincent [email protected]) Fri May 09 1997 23:48

    Do we have any kind of support for telephony type power supplies
    (-48V,-27V etc...)   Is there some way to connect an external telephony
    power supply and have it switched off when the enclosure switches
    off? (safety requirement).
    
    Since the takara won the best of show at the computer telephony
    expo 97, is it reasonable to assume they can actually be used
    for telephony applications?
    
    Do we or an other PSU vendor have a solution for this partner? 
    We are talking quite a few units here.
    (see mail below:)
    
    Thanks,
    
    Vince.
    
    Customer mail follows: ( I sent him the power specs for our Lego PSU)
    
    Thanks for the prompt info. The power supply from the 20 slot backplane
    is beginning to sound interesting. Does it fit into the smaller
    backplane too? I think that a 10-14 slot backplane is more in line with
    our system size, but we need more than 300ma of -5V. 
    
    I'll explain more, My 24 port LS station interface card draws 285ma at
    -5V. Therefore a standard supply will only run 1 card, and only
    marginally if there is anything else using -5V. A 1A -5V supply will
    run
    3 such cards, which is a usable number, even though I am looking for
    more like 4-5 cards. A typical system would have about 4 to 6 telecom
    cards plus the rest of the PCI computer boards. So a 10 to 14 slot
    backplane is about right. But a 20 slot rack mount system will also be
    used for high end systems, just not in as large a quantity.
    
    -48V/-27V is used by the station interface cards to feed power down the
    telephone line to power the telephone set. Ringing is 90Vrms sent down
    the telephone line to make the phone ring. Obviously these are basic
    requirements for a telphony server. Often the -48V and Ringing supply
    are designed to fit into a standard drive bay. These are available from
    many suppliers. The trick is that when the PC power supply is turned
    off
    the telephony power supply ( -48V and Ringing ) must be turned off too.
    For safety tests, when you shut down the PC supply and open the case to
    swap a board there can't be -48V and 90Vrms live in the system. 90Vrms
    give you quite a buzz when you accidently touch it!
    
    The problem can be solved by connecting the telephony power supply to
    the switched power outlet on the supply. BUT, most power supplies no
    longer have one! Do your power supplies have a switched outlet anymore?
    Can your engineers come up with another mechanism to shut down the
    telephony supply when the PC supply shuts down?
    
    I am looking at 200 -300 next year, and maybe 500 to 1000 the year
    after
    that.
    
    Any help  you can offer for these problems is appreciated.
    
    Thanks
    
    Robb Flegg
    
    PS: I should mention, in case you are not aware, that this is part of a
    joint venture that Mitel and Digital have been working on the the last
    year and a half. It's called the mediapath telephony server. Digital
    has written a unified messaging application that runs on this server. 
    It is currently an Alpha, and we are going to come out with an Intel 
    version too. Can you put Alpha processor in these passive backplanes. 
    All of the Telephony cards are ISA right now though.

T.R	Title	User	Personal Name	Date	Lines
223.1	In a PC store near you - but is it "safe" ?	BBPBV1::WALLACE	john wallace @ bbp. +44 860 675093	`Sat May 10 1997 11:44`	17
	Hi Vince, Have you already rejected the off-the-shelf PC world answer to this one? You can buy smart power bars that sense when what's plugged in to Socket One is switched on, and switches all the rest on too. And when Socket One goes off, so do the rest. Including the ring current generator, the monitor, whatever. I have no direct experience, just seen the adverts. However, given that we're also mentioning "safety" here, I'd rather see a proper engineered solution if one was practical. regards john
223.2		GONE::PIERSON		`Mon May 12 1997 15:18`	8
	nothing exists for the existing products, that i am aware of. Consideration is being given to 48vdc for loma/pluto... Expressions of interest from customers are important. regards dwp
223.3	Smart power bars???	MQOOA::LEDOUX	Vincent [email protected]	`Tue May 13 1997 14:01`	14
	re: 223.1 Hi John, I am not familiar with these smart power bars. I have the latest computer shopper and I also looked on the web using keywords like smart+power+bar etc... and could not find any information. Do you have a pointer? Company name?, phone? Is it available in 120V? etc... Thanks for the answer. Vince.
223.4	Remote power down effect?	MQOOA::LEDOUX	Vincent [email protected]	`Tue May 13 1997 14:19`	25
	re: -.2 Hi Dave, My input on the lego power supplies is that they should all have a switched 120V output, like the one in the suckle box. There is always limits to the output current, but if well documented, this should not cause any problem would it? Also, I am probably very dumb, or english not being my primary language, I do not understand page 2-5 in the EK-A0903-IN ETM33 OEM info for the ETMXB-BB backplane. In clear, would it be possible to add a switch to force down the Power Down signal of J16 and actually shutdown the box (except the 5V_aux)? The customer requires that opening the cover of the enclosure causes a power down. Can I assume J16 is there for that? Thanks, Vince.
223.5		GONE::PIERSON		`Tue May 13 1997 15:28`	49
	Vince: > My input on the lego power supplies is that they should >all have a switched 120V output, like the one in the >suckle box. They don't. Notably the 20 slot enclosure aux output is not switched. >There is always limits to the output current, but if well documented, >this should not cause any problem would it? Depens on what purpose is spalnned.... >Also, I am probably very dumb, or english not being >my primary language, 'salright. I speak a dialect of English called 'murrican. >I do not understand page 2-5 in the EK-A0903-IN ETM33 OEM info for the >ETMXB-BB backplane. In clear, would it be possible to >add a switch to force down the Power Down signal of >J16 and actually shutdown the box (except the 5V_aux)? The backplane provides connectors for this. Whether a given PSU supports that is another matter. Implementation dependent. DMCC bits are _components_, some of which have functions in them that others may not fully utilize. The INTENT of the remote shutdown was to allow an SBC to shut down the PSU, (if the PSU allows) If the SBC 'sees' an overtemp. Ferinstance, no provision is made for cabling the psu shutdown signals out of the enclosures. >The customer requires that opening the cover of the enclosure Which 'the enclosure'? >causes a power down. 20 slot enclosure has a built in 'lid open' interlock (You can find them in the lab, by the screwdriver shoved in there...8)>)). None of the others do. Its provided in the 20 slot becasue there is a safety/regulatory requirment, that kicks in at that power level. The smaller boxes do not have interlocks. >Can I assume J16 is there for that? J16 is an option, if a an OE, choses to use a PSU that supports SBC control of the PSU, as above. The safety interlock switch is hardwaried into the mains wiring. regards dwp
223.6	vague starting points for further research	BBPBV1::WALLACE	john wallace @ bbp. +44 860 675093	`Tue May 13 1997 22:21`	19
	Hi Vince, If your Computer Shopper is anything like UK "Computer Shopper", you need to go upmarket some. Try the back pages of Byte, perhaps (but my only 1997 one doesn't have anything). Cybex? Circuit City ? Jameco (see Byte?) ???? local US input would help here, even if it's to say that I've been imagining things! See also the "computer supplies" catalogs from folks like Inmac, and Misco. There, these are sold "own brand" and are probably indexed under "surge suppressors" (one multi-socket surge suppressor with one "smart" socket that detects when what it's connected to is powered up). Sorry I can't be more definitive. If desperate, you could probably ask in the IBM-PC notesfile and see if anyone more local than me can help. regards john
223.7		GONE::PIERSON		`Thu May 15 1997 18:03`	11
	possible clarification to .5: Both the '14 slot' and '19 slot' PSUs have provision for 'remote' shutdown. This is INTENDED for use only by the Alpha SBC Server Management function. If desired, it COULD be reengineered by a _technical_ OEM for other functions: eg remoted, rack wide, power down. regards dwp