Classic Rotary Phones Forum

Telephone Switching => Key Systems (Electronic, 1A2 etc) => Panasonic (PBX) Key Systems => Topic started by: trainman on March 27, 2011, 01:04:56 PM

Title: Panasonic PBX Power Supply Modification
Post by: trainman on March 27, 2011, 01:04:56 PM
Hi All, I  wanted to use the Pnsonic PBX simply to connect two phones together in-house, but not to an outside line.

I don't want the pbx powered up 24 hrs. I was rhinking of some kind of relay to turn the unit on when you pick up one phones receiver. So, I was wondering, if there was  contact on the hookswitch that could make when picked up to power a rely coil, to turn on the unit.

I don't know if it would work, because first, I hve no idea what voltages and currents the phones work from. THen finding a proper coil. THen, there is power requirement of the relay coil, and there simply may not be enough of it on  long run of wire to operate the relay coil.


Any thoughts? Godd idea or bad?
Title: Re: Panasonic PBX Power Supply Modification
Post by: Owain on March 27, 2011, 01:39:21 PM
You could do this, but you would have to modify the telephones (I presume you're using standard phones) to bring out hookswitch contacts, use either a mains power supply or a battery as power supply to a relay to switch the mains.

Then you'd have to wait for the Panny to go through intialisation and set-up every time.

If you just want a ring-down circuit for an intercom then use that.
Title: Re: Panasonic PBX Power Supply Modification
Post by: gpo706 on March 27, 2011, 02:10:59 PM
Just leave the Pana on, its by far the easiest solution.
Title: Re: Panasonic PBX Power Supply Modification
Post by: trainman on March 27, 2011, 02:12:59 PM
I forgot about power to the rely coil. Then I thought bout mounting a small microswitch or simmilar to act when the hookswitch is raised or lowered. But I would to find a smll current draw relay coil because dry-cell power supply would be easist.

I didn't want to lweave it on all times because it would see little use, and i figure it would extend the life of the unit.
Title: Re: Panasonic PBX Power Supply Modification
Post by: Owain on March 27, 2011, 03:59:19 PM


I didn't want to lweave it on all times because it would see little use, and i figure it would extend the life of the unit.

Voltage surges at switch-on are more likely to shorten the life of the unit.
Title: Re: Panasonic PBX Power Supply Modification
Post by: Phonesrfun on March 27, 2011, 06:54:28 PM
Owain has a definite point about the power surges.  He also has a point about it not being instantaneous in coming on.  It probably goes through about a 15-second boot-up sequence.  Best to just leave it on.  It sure does not take any appreciable power.  Mine is on 24/7 and I must say that I surely cannot see a difference in my power bill.

Title: Re: Panasonic PBX Power Supply Modification
Post by: bingster on March 27, 2011, 11:55:32 PM
Try keeping an eye out for one of these:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180641585154

That particular one is outrageously priced, but I got mine for around $25.  It's perfect for quick and easy point to point calling using any two standard telephones, and is also very handy for testing purposes.
Title: Re: Panasonic PBX Power Supply Modification
Post by: Brinybay on March 28, 2011, 01:17:45 AM
Not sure I'm getting this.  Why don't you want to leave the power on?  I have a Panasonic 308.  To reach another extension, I just dial the extension.  That will work with or w/o a line going in.  But the power does have to be on.
Title: Re: Panasonic PBX Power Supply Modification
Post by: trainman on March 28, 2011, 01:42:51 AM
i didn't want the power on all times because unit would be used infrequently, and I thought it would prolong the life of the unit by not keeping it powered up at all times.

I don't think it would be used enough to justifiy it being on at all times.

It's only a novel way to call my downstairs  flat neighbor(cousin), and be able to dial the rotary phones,  but we're only home at the same time on weekends, hence the infrequent use.
Title: Re: Panasonic PBX Power Supply Modification
Post by: Owain on March 28, 2011, 07:21:53 AM

It's only a novel way to call my downstairs  flat neighbor(cousin), and be able to dial the rotary phones,  but we're only home at the same time on weekends, hence the infrequent use.

If you really want to, use a 7-day timer on the mains supply and set it for weekends only.
Title: Re: Panasonic PBX Power Supply Modification
Post by: GG on March 28, 2011, 08:22:08 AM


Power consumption on these is relatively low and would only be a serious concern if you're on off-grid power (solar).  I tested all of them with a Kill-A-Watt meter a while back and found that the lowest power consumption of any of them was the KX-TD 308, a relatively obscure model that didn't sell a whole lot and came equipped for 4 extensions expandable to 8.  I have one and I'm not planning to sell it, as I might be off grid at some point. 

However, for sheer energy efficiency and minimum eco impacts, for an intercom system among two to five stations, nothing beats a good ol' magneto phone system.  Use coded ringing for any more than two stations.  Power the phones' transmitters with two D batteries in series.  Use rechargeable batteries, keep some charged ones on hand for replacing discharged ones when needed.  Get a solar charger if you want to go that far, but otherwise, a conventional charger for those will still use relatively minimal power.   (This is better than powering the transmitters with AC adaptors, which will always be drawing some mains power even when the phones are not in use.) 

Used as an intercom system that way, with more than two stations, you'll need to have the number labels printed with the ringing codes, e.g. "Answer 1 long ringn + 1 short ring" and "Answer 2 short rings," etc.  Just as it was back in the day of heavily loaded rural party lines. 
Title: Re: Panasonic PBX Power Supply Modification
Post by: gpo706 on March 28, 2011, 08:29:23 AM
Try keeping an eye out for one of these:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180641585154

That particular one is outrageously priced, but I got mine for around $25.  It's perfect for quick and easy point to point calling using any two standard telephones, and is also very handy for testing purposes.

Thats a neat gadget, but not nearly as fun as Panasonic!  :)
Title: Re: Panasonic PBX Power Supply Modification
Post by: Wallphone on March 28, 2011, 09:17:54 AM
The Micro Seven is a product similar to what Bingster posted, > http://bit.ly/idIsEv < and comes in 2 and 4 line models. Be patient and you can get one for around $30, and there is a manual for it Online.
Doug Pav
Title: Re: Panasonic PBX Power Supply Modification
Post by: trainman on March 28, 2011, 11:48:05 AM
I don't have any magneto phones. THose would be more fun, I suppose.

Can one wire 500 type phones to work from battery?  WHat's the lowest voltage they will will recevie/talk on?
Title: Re: Panasonic PBX Power Supply Modification
Post by: Owain on March 28, 2011, 12:14:27 PM
I don't have any magneto phones. THose would be more fun, I suppose.

Can one wire 500 type phones to work from battery?  WHat's the lowest voltage they will will recevie/talk on?

circuit here  (http://www.ee.washington.edu/circuit_archive/circuits/F_ASCII_Schem_Tel.html#ASCIISCHEMTEL_010)
Title: Re: Panasonic PBX Power Supply Modification
Post by: Phonesrfun on March 28, 2011, 03:33:35 PM
Can one wire 500 type phones to work from battery?  WHat's the lowest voltage they will will recevie/talk on?

For a two-phone intercom, all you need is a battery in series with the two phones.  However, the reason a magneto phone was suggested is that a 500 has no way of ringing the other phone.  You cannot do that with just a battery.

A battery holder from Radio Shack that holds two 1.5 volt batteries is ideal for hooking 2 phones in series.  You only need three volts for it, and depending on the amount of usage, and the size of batteries used, it will last quite a long time.  For the longest life of batteries, you can get a battery holder for 2 size "D" cells.  3 volts is pretty much an ideal voltage in series over a short distance.  You askes what the lowest voltage is....  Well, since the smallest regular battery is usually 1.5 volts, that would also work, but you might find it too weak.  I suggest 3 volts.  The absolute value of the voltage is not really important in this case.  You could even use a 12-volt car battery, but that would be overkill.

But, like I mentioned above, without a separate source of ringing current, you will have to either agree on a schedule, bang on the pipe, shout out the window, or call them up on a regular phone or cell phone and have them meet you on the intercom.  You could also run a separate line for a buzzer circuit.

Title: Re: Panasonic PBX Power Supply Modification
Post by: trainman on April 02, 2011, 01:27:43 AM
Hi all, thanks for the suggestions.

I think I'll look for a couple of workable mgneto phones for the "phone system"
Title: Re: Panasonic PBX Power Supply Modification
Post by: GG on April 02, 2011, 07:31:48 AM


The Micro Seven has the interesting feature of an amplitude and frequency adjustment for the ringing, from little screw type trimming resistors accessible via holes in the bottom of the unit.

Yes that means you could use a bunch of phones with harmonic (frequency selective) ringers, as long as they were all the same frequency (good luck! : - )

Though, some of those are selling for prices that'll get you a Panasonic, new.

---

The two-way ringdown circuit thing shows a label by the power cord saying it uses 30 watts.  That's more than a Panasonic PBX and for what it does, it's an energy hog if you leave it plugged in all the time. 

---

Re. 500 sets as intercoms:  Another cheesy phone mod I used to do in highschool was to turn these into common-buzz intercoms as follows (it's been @ > 30 years since I did these so this is from memory and may not be correct):

Attach an Edwards DC buzzer from L2 to G, where the red & black wires from the C4A ringer are connected.

Wire across F and RR to jump the dial pulse contacts.

Take the white (off-normal) dial contacts and wire them across L1 and G. 

Connect all the phones together using 3-conductor wire: all the L1s together, all the L2s together, all the Gs together.

Connect a DC source sufficient to buzz all the buzzers, across L1 and L2. 

Now when you turn the dial, it connects DC to the buzzers and all the phones buzz, for common signalling and common talking. 

Assign different buzz codes to each phone.  Typical would be a 4-station system with:  Short-Short, Short-Long, Long-Short, Long-Long.  Dial a low digit such as 2 for a short buzz, and a high digit such as 8 for a long buzz. 

A system like this works well for e.g. a household of four people, because you give buzz codes to the people rather than the phones, and the people can answer from anywhere.   E.g. Alice = Short-Short, Bob = Short-Long, etc.  To get more than four people, use three buzzes, e.g. Short-Short-Long, etc.

And of course all the cheesy phone mods can be undone and the phones put back to being regular 500 sets any time. 

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Alternately, AE 87 or 187 sets, with the little Signal button, can be used nicely for 2-line sets with the 3d line used as Intercom with non-selective buzz.  With DC buzzers, this adds up to seven wires, which will run on 4-pair and you can use Ethernet plugs & jacks to make it easy to do. 

The problem nowadays is finding "nice sounding" DC buzzers that are telco quality, and ideally that are small enough to fit inside the telephone sets.  Alternately one can use a 5-wire circuit for intercom, whereby two wires are DC for talking, and 3 wires are AC for running those little round 1A2 station buzzers, which are telco quality and nice sounding (for buzzers anyway, heh)   However, a 5-wire intercom circuit means that two lines + intercom = 9 wires, thus can't be accommodated on 4-pair. 

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iMHO for residential use for households up to @ 4 people, common talk & common signal makes the most sense.  You want to talk with Bob who could be in his bedroom or in the living room or somewhere else.  You don't want to call his bedroom and then call the living room and ask Alice who is in the living room where Bob is and then she says you need to call the garage because he's working on something out there and blah blah blah...   Faster to just press the little signal button once long and once short, and then Bob answers and says "I'm in the bathroom, I just got out of the shower," thereby proving the age-old rule that the surest way to make the phone ring is to go to the bathroom or be washing dishes with your hands all full of soap suds. 
Title: Re: Panasonic PBX Power Supply Modification
Post by: GG on April 02, 2011, 08:03:11 AM


How to use a Panasonic PBX for "calling by person rather than by room":

Hook up external paging speakers.  There are self-amplified types that run on 2-pair, where one pair is audio and the other is common 24 vDC power, Valcom make these. 

There are also desk speakers that look a little like oldschool radios without tuning knobs.  If they make 'em in red, you can pretend you're living in North Korea and that's the obligatory 1-channel government propaganda feed ; - )

Dial the "page code" to page through all the speakers, telling the person you want to reach to pick up any phone and dial the "page answer code."   When you dial the page code, the speakers go beep-beep and then you can talk over the speakers.  For example, "Alice, dial 123" (or whatever the code is).  The person you're calling goes to the nearest phone and dials the page answer code, and they're connected to you. 

You may have to tweak the numbering plan to get rid of the pesky * at the beginning of most of the feature codes, and shorten the dialing codes for the things you use most often such as page and page-answer. 

If there's demand around here for these, I could start providing them: new Panasonic systems with numbering plans tweaked appropriately for dial phones.  (I've been saying for the last couple of months that I'd post a price list for Panasonic PBXs, and the 1st Quarter insane workload is almost over so I should be getting to this soon.)  (Tonight I've been posting here while remote-programming new extensions for a client that's been growing by batches of 25 phones at a time.  Four more voicemail boxes to go...)  (Eric, I still haven't forgotten your AE speakerphone; I'll get it packed this weekend and ship next week.)