Help me in my project:building a 1 to 4 PBX system!

[nero]

i need u to help me choosing the components such as the micro controller and SLIC's and ADC's and idea for the general block diagram for the cct[/SIZE]. for the 1 to 4 pbx system..it's required that:

The users of the switching system should be able to call one another, and be able to reach an outside line by pressing the digit “9” at the beginning. The 4 stations numbers are:
• Station 1: 112
• Station 2: 243
• Station 3: 236
• Station 4: 136

Specifications:
• The system should give station 1 priority over all stations (if all lines are busy any station 1 calls an outside line or another busy station, this line should be freed by force).
• The system should operate on a real telephone line system.
• Any user can call another user or reach an outside line.
• When calling another user, the other user phone should ring.
• Circuit switching (analog)

look guys here is what we think it's gonna be and i want all of u to set me straight if something i propose is odd..okay?:
we will connect each phone of the four lines to a DTMF that will convert the digits pressed into digital signals sent to the microprocessor and there will be a cct to make the dial tone and a cct for the ringing...that's what we came to so far..i need a VERY SIMPLE block diagram for the rest of the cct showing me the connections between the microprocessor and the ringing and the dial tone generator ccts and sombody talk to me about the SLIC's and what do thay exactly do cuz some people said that we may use it...thanx so much
this is for people with good knowlege of PBX and who dealt with them b4 and love the challenge ,,,i will appreciate the help so muchhhhhhhhhh

 

[(*steve*)]

How much are you prepared to pay us to do this?

 

[nero]

a thank u....i just needed hints about the components and the schematic of the cct.!

 

[davenn]

a thank u....i just needed hints about the components and the schematic of the cct.!

uh huh ya think

mmmmm with the time and work involved $50,000 may be almost enough

you are looking at a very complex project, there are already a number of commercial systems around that will do what you ask

Dave

 

[nero]

uh huh ya think

mmmmm with the time and work involved $50,000 may be almost enough

you are looking at a very complex project, there are already a number of commercial systems around that will do what you ask

Dave

who said im looking for a commercial one!..if i wanted i 'd have bought one!!!...it's just a lab project not even a graduation project guys..so for gods sake!!!

 

[(*steve*)]

it's just a lab project not even a graduation project guys..so for gods sake!!!

In that case it belongs here.

Read and heed the notice.

 

[JimW]

I have built one like you descibe. Even with an extensive backround in telephony, and a top notch software engineer backing me, it took 6 months to fully functional prototype. Complicated does not begin to describe what you are looking at doing.

You can always start with the data sheets and appliation notes of Mitel (hmm, maybe it is Zarlink today). but if you don't understand the issues of fully isolated phone lines, you will have a lot of trouble connecting any digital/analog PBX to telco POTS lines. Buying off the shelf SLICs will help, but will really dent your pocket book. Also Google "analog PBX chip" and you might find something there that can get you headed in the right direction.

IF you want to cheat, I would approach this with some concept of a relay based cross bar switch that ties phones to other phones or to the telco lines. When it is phone to phone, you will need to synthesize the telco current loop to the phone. This is essentially a phone based intercom. More complicated because you want to be able to make the phones ring. A telco ring generator circuit is not too difficult, but you need to route its output to the desired phone line and then look for the remote phone off hook current draw to know when to stop the ring and engage the connection relay. Proably not more than a few weeks work for someone who had done it before and knows exactly what they are doing.

 

[davenn]

Thanks for the backup Jim, nero didnt seem to understand what he was asking
I'm also from the telco industry, having worked on and installed many PBX systems over the years

What he wanted was no 5 minute project and like you also know would take a very long time and much expense to achieve
Ohhh gosh Mitel, thats a name I havent heard in the last 20 yrs since being out of the industry. It was very popular for the larger systems 6 incoming lines and 20 extensions and up.

One small unit popular with small businesses was a system called the SBX6 2 lines and 6 extensions, there was also an SBX8 and 12. Not sure if they were in use outside of New Zealand or not. But were extensively used by Telecom NZ during the '80's
I cut my 'PABX' teeth on those systems

Actually I still own an SBX6, had it running in my own home for all of the '90's before leaving NZ.

Dave

 

[nero]

@jimw....thanx for ur useful advices ..see..u r the 1st one to give me a useful tip instead of keep saying how hard my project is...if it's that hard?,.,why would they give it to the third year (pre-last) communication students who have didn't have any solid courses in it?
..i guess cuz they know we can do it by simply searching and reading and having an extra help...well...i am asking for help now!...look guys here is what we think it's gonna be and i want all of u to set me straight if something i propose is odd..okay?:
we will connect each phone of the four lines to a DTMF that will convert the digits pressed into digital signals sent to the microprocessor and there will be a cct to make the dial tone and a cct for the ringing...that's what we came to so far..i need a VERY SIMPLE block diagram for the rest of the cct showing me the connections between the microprocessor and the ringing and the dial tone generator ccts and sombody talk to me about the SLIC's and what do thay exactly do cuz some people said that we may use it...thanx so much

 

[LTX71CM]

Is the requirement specifically that you design the hardware or just complete the task? A SIP box and scrap computer loaded with Asterisk would work nicely.

 

[nero]

yeah man they want the complete hardware ccts! (