sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Lkg for a diode matrix

Sure wish I would have saved my boxes and boxes of 1A2 stuff I started collecting in the late 70's ... but after 20 years, it was time to toss out all the old AE bile green sets, 3 and 5 row Bell System Property Not for Sale Call Directors (dial too!), 207C's, even stuff as modern as an ITT 501 And who remembers the 400B line card along with the 584 panel with ceramic edge connectors?

Anyways... I have a HVAC system with 30 heat pumps, all with individual timers. At most, we require just 5 different time settings, including one for the cooling tower.

Spending twenty grand on a controller is kind of goofy, and would be way too hard for the building maintenance guy to set (si habla espanoel anyone?).

So.... why not use a couple of the 13x5 (I swear I've seen em, made for 584 panels) diode matrix panels off 5 timers ... changing a heat pumps cycle would be as simple as moving a diode pin.

Solves the problem, and is even something a person of limited technical ability can figure out.

Somewhere out there, someone has a few of these sitting on a shelf... any leads would be appreciated!

Thanks
Dave

My only concern is that HVAC controls use 24 volts AC. Diodes do a great job of routing DC, but with 1A2, a lot of it has to do with the capabilities of the ringer and it's bias spring at only 30CPS AC. Granted, you can use DC for these controls since an AC contactor will respond to AC or DC, you'll likely need a pretty hefty DC power supply to support a myriad of 30 heat pumps.

The factory matrix blocks (1A1) are quite long-gone, although I did see some of the ones made by Plant Equipment on e-bay a while back that use DIP switches. It might not be a bad idea to search Plant Equipment over at e-bay and see if they are still around.

Any applications that we have these days involve the use of a split 66 block with diodes connected across columns B and C. Then, columns A and D become tie points where the trickery is done.

Is this what you are looking for? Since you're doing AC you could replace replace the diodes with wire to make them shorting plugs. (And yes, the one on the right *is* still working.)

wow. i have no idea how that works

For KTS. When a line rings, AC is applied to the ringing leads. Goes thru the diode to become pulsating DC on the Common Bell lead. The diodes on other numbers also attached to the same common bell stop the pulsating DC from going back on other ringing leads.

This allows you to have 13 phone lines on 6 sets of 9 line phones with only the lines on the phone ringing the phone.

On KTS, ringing is optional, at extra cost.

Gotcha

Like mike said, if no matrix was built then you would end up with a term called phantom ringing on other sets that did not own that particular line.

The diode acts as a traffic cop and allows ringing voltage to pass to the desired set or you could look at it as blocking a half wave of ringing current.

Isn't it actually a capacitor that's blocking the dc voltage instead of a diode?

Nope it's a diode, blocking the ac ringing.

Bill is correct: A capacitor is actually blocking DC flow but allowing AC to pass through. A diode blocks DC in one direction but allows it to pass in the oposite direction. Since AC reverses polarity 30-60 times per second, a little bit can get through a diode as long as there isn't a capacitor associated with the ringer. That capacitor must be bypassed, otherwise, it would absorb the trickle of ringing that gets through. In many cases, the bias spring for the ringer also needs to be shifted to the low position since much less ringing voltage is getting through.