Search results

  1. Alpha2

    Link Ring Trip Circuit Ommission

    Folks, While browsing through my collection of Link circuits online the other day, I noticed an ommission of the Ring Trip cct on the Link A2B+1 DTMF design. Shown below the main cct is the RT cct, composed of the relay RTR/2 a diode and the AC voltage source (between 30 and 40 VAC is usually OK...
  2. Alpha2

    New Link Updates online some time soon

    Folks, the Link P design has been finalised and those of you who are waiting in telephone land can be assured that it will work (I made it work reliably only last week!) and once again follows the simple design philosophy of simplicity and "off the shelf" components - no special chips or fancy...
  3. Alpha2

    Notes on the Link intercom

    Folks, the transformer depicted in the diagrams is a simple audio style transformer, with a 1K centre tapped winding (for the phone handset side of the cct) and an 8 ohm winding, which is used to couple dial tone, ring tone and busy tone (where it's used) from IC1's output pin 5, to the caller...
  4. Alpha2

    New Link Updates online some time soon

    Hi folks, It's been a while since I last posted to all you hyperboreans out there in telephone land, but nevertheless, I've been tinkering (read 'Linkering') at my workbench and I've got 2 new link designs to share with you some time soon. The first one has been designated the "Link P" and the...
  5. Alpha2

    Notes on the Link intercom

    Folks, terribly sorry to not have answered any of you for so long, but I was away from my normal surroundings for quite some time (not in jail or anything) but to answer a couple - no I don't know where you can get the MC 45436P IC from in the US or Canada. You can mail order them from DSE or...
  6. Alpha2

    DTMF transceiver connection

    Just use it the way I've described it to you up above in the first response to your question. I can't see why the transformer coupling won't work, whether it's the MT 8870 or the MC 45436 chip, or it's a transceiver (both ways) device. You may have to identify a pin on the chip which alternates...
  7. Alpha2

    Timer Circut Help

    Find yourself a good tutorial on the NE 55 timer chip on the Net (there's a few good ones around). Basically, the 555 chip in its 'monostable' mode has what you are looking for. Pin 2, held to +ve rail via a 4.7k resistor, is switched momentarily to ground to turn the timer on. Then pin 4, which...
  8. Alpha2

    Optical Private Branch Exchange

    Have a look at The Link Telephone Intercom (posted as project number 13 under 'Telephone Related') this may give some clues as to the basics of telephony - it also uses a couple of opto couplers - the closest I could get to an optical PBX using off the shelf parts :-) Alpha
  9. Alpha2

    DTMF transceiver connection

    Have a look on the Net for the MT 8870A DTMF Transceiver by Mitel Corp. Look for a data and applications info sheet, this whould help yo a lot. Alpha
  10. Alpha2

    DTMF transceiver connection

    Hi there, connecting a DTMF device to an active phone line can be tricky. For starters, you've got arond 50 volts DC on the line when it's idle (phone is 'on hook') then you've got around 80 to 110 volts AC when the phone is ringing (interrupted) and around 5 to 12 volts when the phone is picked...
  11. Alpha2

    Notes on the Link intercom

    Folks, I noticed that there's been some 86 members look at the Link design, but so far, no replies. Can someone, anyone email in and tell me what you think? I'm always open to suggestions as to better ways of doing things. I'm also wondering if anyone's actually built one up? even if it's just...
  12. Alpha2

    Notes on the Link intercom

    Some extra notes for those attempting to build the Link intercom: 1. Best to build it up on your SK-10 panels to ensure that all parts are working, before you go soldering them to a board. 2. Adjust R6 by making a call, then taking the called party's handset off hook - adjust R6 until the ring...
Top