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Old 24th Aug 2022, 7:21 pm   #1
OscarFoxtrot
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Default Practical Electronics mag - Telephone exchange project

Practical Electronics should be publishing design for a mini telephone exchange for using old phones as intercoms in the next - October? - issue.
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Old 25th Aug 2022, 6:35 am   #2
dagskarlsen
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Default Re: Practical Electronics mag - Telephone exchange project

Nice to know, I have got a Panasonic KXT 616 and so far it works great, but it is harder and harder to get all you need. :-|
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Old 25th Aug 2022, 8:26 am   #3
JohnBHanson
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Default Re: Practical Electronics mag - Telephone exchange project

I have two of these panasonic telephone exchanges but not working very well - would you happen to have circuit diagrams per chance?
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Old 26th Aug 2022, 5:35 am   #4
dagskarlsen
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Default Re: Practical Electronics mag - Telephone exchange project

Sorry, no documentation :-(
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Old 26th Aug 2022, 7:32 am   #5
VintageTel
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Default Re: Practical Electronics mag - Telephone exchange project

Quote:
Originally Posted by JohnBHanson View Post
I have two of these panasonic telephone exchanges but not working very well - would you happen to have circuit diagrams per chance?
616 Manual here:
http://www.classicrotaryphones.com/f...php?topic=3082

Other model Panasonic manuals there also. Informative site, worth bookmarking.
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Old 26th Aug 2022, 12:17 pm   #6
Roger Ramjet
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Default Re: Practical Electronics mag - Telephone exchange project

Thanks - that's interesting & worth a look.... Practical Wireless did an article many many moons ago that allowed connection of two telephones using relay logic to switch the ringing current. I wonder if the PE article uses electronic switching with multiple extensions ?
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Old 27th Aug 2022, 4:56 pm   #7
OscarFoxtrot
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Default Re: Practical Electronics mag - Telephone exchange project

AFAICS from the brief description, switching with multiple extensions.

The two telephones with relay logic was described here

https://www.vintage-radio.net/forum/...8&postcount=20

Cook Abbott - Electronics and Wireless World.
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Old 16th Sep 2022, 9:10 pm   #8
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Default Re: Practical Electronics mag - Telephone exchange project

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Originally Posted by dagskarlsen View Post
Nice to know, I have got a Panasonic KXT 616 and so far it works great, but it is harder and harder to get all you need. :-|
possibly only available from Panasonic, but the 616 is actually a dual 308 with the first board only having the lower extension numbers( 21-28) and the ability of ext 21 to program the system. For most obscure problems Panasonic would recommend removing he battery and a power reset to purge the memory of any gunge. Then replace the battery and reprogram.
For both 308 and 616 there were two programing masks for ext 21. The main difference was in the store /memory key, depending on which handbook/ Display phone you have. you have
Button in question is the bottom right hand one. One of my "round tuit" tasks is to find my 308/616 course handbooks and make a list of the things we learned at Panasonic training places that do not show up in the manuals .
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Old 23rd Sep 2022, 7:17 pm   #9
OscarFoxtrot
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Default Re: Practical Electronics mag - Telephone exchange project

This is now in WHSmith.

It's a two-line ringdown circuit, not a dial intercom. Although very nice, with selectable UK / AUS / other ring cadence, various options for transmission bridge etc, it's rather complicated for anyone just wantting to run a couple of phones, and there are no options for dialling or more than two phones.
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Old 23rd Sep 2022, 7:34 pm   #10
Roger Ramjet
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Default Re: Practical Electronics mag - Telephone exchange project

Quote:
Originally Posted by OscarFoxtrot View Post
This is now in WHSmith.

It's a two-line ringdown circuit, not a dial intercom. Although very nice, with selectable UK / AUS / other ring cadence, various options for transmission bridge etc, it's rather complicated for anyone just wantting to run a couple of phones, and there are no options for dialling or more than two phones.
Ta for the info Oscar.... might be useful as a telephone tester ? Will try to ge a copy.

rog
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Old 28th Sep 2022, 7:14 pm   #11
Roger Ramjet
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Default Re: Practical Electronics mag - Telephone exchange project

Got copy of the mag today & was stunned by the complexity & number of components required for this kit so will go back to plan A which uses two relays, a capacitor & a 75V / 25Hz source.

I will create a new post in the appropriate section offering the magazine FOC to anyone who might be tempted to take a punt.

Rog
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