Integrating Cordless Phone and Clear-Com Partyline System

[memoguy]

Hi all!

So, at my school we have a clearcom wired system. It is very nice, but we would like to have some wireless capability. We have a load of wired beltpacks for which we do not have headsets. So, here is what I am thinking. Take a cordless phone. Take the audio output/input connections on the phones basestation, and wire them to the headset input/output of one of these disused beltpacks. Then, simply press the answer button on the cordless phone, and hay presto, you are in business. I could then get headsets for the cordless phones, to make them a bit more theater friendly.

I am not sure about what kind of voltages I would be looking at here, but I suspect that is may be necessary to employ a transformer (if there are impedance matching issues) or a voltage divider (if there are over voltage issues). This idea is in the very early stages, so I have not fully researched the voltage/impedance matching stuff, but I am just interested in what you guys think of this as an idea?

 

[memoguy]

Any of the clever people of CB have any thoughts?

 

[porkchop]

I'm not a sound guy, but I would guess that's either not going to work or be too heavy/expensive/time consuming to really work well for you. If you really want to mess with it though make sure you ask permission before you start, keep whoever's in charge updated on what you're doing, and don't modify the packs themselves.

 

[memoguy]

I'm not a sound guy, but I would guess that's either not going to work or be too heavy/expensive/time consuming to really work well for you. If you really want to mess with it though make sure you ask permission before you start, keep whoever's in charge updated on what you're doing, and don't modify the packs themselves.

Hi there!

In terms of permissions and all, do not fear, I have that all sorted. We have gear that has been written off that is essentially the exact same thing as our operational system. I am going to use this written off gear to test, and that has been cleared with the powers at be.

Too heavy - not certain what you mean by that?
Too expensive - only looking at buying a $40 phone, a 4pin XLR, a couple of resistors and perhaps a transformer
Too time consuming - That is a fair point, however I am about to go on 10 weeks of holidays, so I think I will be able to find the time It is a bit of a fun project for me.

Thanks for your feedback, I want to hear about everything that people think could go wrong so I can try an remove those issues in the planning stage!

Thanks!!

 

[len]

If you want to use cell phones, you should have these http://www.whateverworks.com/itemdy...ign=datafeed&gclid=CN2q8-GG8boCFcRi7AodBxQA9g

 

[Floobydust]

In the US, there are "party line" or "conference" phone numbers that multiple cell phones can call and everyone can talk to everyone else.

Not me, but there are people here that know the innards of the ClearCom system. Keep us posted.

 

[sk8rsdad]

We used to do this with a home built box. I will see if I can get the fellow who built it to hunt up his specs and get them posted.

 

[memoguy]

Thanks all!

Re Sk8rsdad - that would be awesome!

Just to clarify for everyone, I am not looking to connect the clearcom system to an external phone line. What I am looking to do is simply connect a cordless phone directly to the clearcom system. There will be no outside connection, but a direct connection from the cordless phone to the headset jack of a clearcom box. I am thinking of doing something like this:
http://web.archive.org/web/20070730071650im_/http://www.vital.pri.ee/PSTN/index_files/Phone6.jpg

and just connecting the speaker out of the cordless phone to the mic in of the clearcom, and the mic in of the cordless phone to the speaker out of the clearcom. The main issue I can see is that there may be feedback, since the phone spec does not separate the input from the output (i.e. you can hear yourself when you speak on the phone). I may need to think about this a bit.

 

[Footer]

Thanks all!

Re Sk8rsdad - that would be awesome!

Just to clarify for everyone, I am not looking to connect the clearcom system to an external phone line. What I am looking to do is simply connect a cordless phone directly to the clearcom system. There will be no outside connection, but a direct connection from the cordless phone to the headset jack of a clearcom box. I am thinking of doing something like this:
http://web.archive.org/web/20070730071650im_/http://www.vital.pri.ee/PSTN/index_files/Phone6.jpg

and just connecting the speaker out of the cordless phone to the mic in of the clearcom, and the mic in of the cordless phone to the speaker out of the clearcom. The main issue I can see is that there may be feedback, since the phone spec does not separate the input from the output (i.e. you can hear yourself when you speak on the phone). I may need to think about this a bit.

Your going to have a ton of issues doing this. The circuit you have there is designed to replace a handset with audio connections (I think). POTS lines have a voltage applied to them to make them work... this circuit does not have the voltage. After that you will have to deal with all the other issues that clearcom can bring up.

In the end while it is a nice idea, odds are getting it to work will be more trouble than it is worth.

 

[memoguy]

Your going to have a ton of issues doing this. The circuit you have there is designed to replace a handset with audio connections (I think). POTS lines have a voltage applied to them to make them work... this circuit does not have the voltage. After that you will have to deal with all the other issues that clearcom can bring up.

In the end while it is a nice idea, odds are getting it to work will be more trouble than it is worth.

Yeah, I just realised that the schem I linked to was not correct. However I have found other example of telephone line interfacing. Most are design for use with a sound card, I think that with minor modification I could make it work with a clearcom. I will keep you all in the loop with my progress.

 

[Chris15]

What about a slightly different aqpproach?
Everything I see in the shops has multiple handsets and the ability to call between them...
So how about using the headset jack on one phone to interface to the comms system and have that in call to another phone?

You'll probably need some attenuation to go from speaker level to mic level each way, and you may need some DC blocking if they are setup for electret mics, but otheriwse, I think it could be far easier than mucking around with getting the 48V onto the phone line that it needs to operate like normal...

 

[memoguy]

What about a slightly different aqpproach?
Everything I see in the shops has multiple handsets and the ability to call between them...
So how about using the headset jack on one phone to interface to the comms system and have that in call to another phone?

You'll probably need some attenuation to go from speaker level to mic level each way, and you may need some DC blocking if they are setup for electret mics, but otheriwse, I think it could be far easier than mucking around with getting the 48V onto the phone line that it needs to operate like normal...

That is a fair point. It will be my backup plan. If I can get my intended system to work it would be ideal as you do not need as many phones to make it function.

 

[sk8rsdad]

We used to do this with a home built box. I will see if I can get the fellow who built it to hunt up his specs and get them posted.

The fellow who built our interface says his design is obsolete for newer systems and would need to be reworked. He suggested an AC-701 would do what our interface box used to do.

 

[Keukleton]

Hi all, im interested in whether anyone can report if this worked or not as i would love to implement this, or something similar in my school

 

[Jay Ashworth]

In *theory*, since a phone and a beltbox are both 4W-2W hybrids that go across a 600 ohm line between 12 and 48VDC, you should be able to just make a mod-jack to XLR3 adapter, and plug the cordless *into the system* as a beltbox.

I've never tried this, mind you. But the electronics shouldn't be incompatible, as I understand all the pieces.

Signal might be troublesome, and Mic Kill certainly wouldn't work (if you have it), but as long as your base PL system is traditional 2-wire analog, this seems worth a try.

 

[Peter William]

The fellow who built our interface says his design is obsolete for newer systems and would need to be reworked. He suggested an AC-701 would do what our interface box used to do.

How old of a system would you be referring to? As my school is trying to do this, and we have an old(ish) Jands Ezicom E200 with E100 and E101 beltpacks.