ken@argus.UUCP (Kenneth Ng) (04/10/90)
Hello everyone, the equipment budget for the department I work in has been slashed to zero, and our line test set got stolen recently. I've been wondering if anyone knows what justifies the $200-300 cost of such a beast. Is it because it is a speciality market, or are there components in there that are really worth a couple hundred dollars? I've added up the cost of the obvious components (headset, tone pad, aligator clips, batteries, isolation transformer) and arrive at about $50. The only thing I don't know about is the monitor option, which is what I use most to debug the modems. What makes up this circuit? One final thing, does anyone know if I can use the telephone isolation transformer on an old 300 baud modem to shave a couple dollars? We've got some 300 baud modems around collecting dust.
bies@sctc.com (Marty Bies) (04/10/90)
ken@argus.UUCP (Kenneth Ng) writes: >Hello everyone, the equipment budget for the department I work in has >been slashed to zero, and our line test set got stolen recently. >I've been wondering if anyone knows what justifies the $200-300 >cost of such a beast. Is it because it is a speciality market, >or are there components in there that are really worth a couple >hundred dollars? I've added up the cost of the obvious components >(headset, tone pad, aligator clips, batteries, isolation transformer) >and arrive at about $50. The only thing I don't know about is the >monitor option, which is what I use most to debug the modems. What >makes up this circuit? Considering that you have $50 in parts. I would think that the time it would take to build and debug the whole thing and make it reasonable to use would far exceed the $200 cost of a new test set. But then, my budget is like a bottom-less pit :) --Marty B bies@sctc.com
larry@kitty.UUCP (Larry Lippman) (04/11/90)
In article <1723@argus.UUCP>, ken@argus.UUCP (Kenneth Ng) writes: > Hello everyone, the equipment budget for the department I work in has > been slashed to zero, and our line test set got stolen recently. > I've been wondering if anyone knows what justifies the $200-300 > cost of such a beast. Is it because it is a speciality market, > or are there components in there that are really worth a couple > hundred dollars? There is nothing sophisticated or expensive in a telephone test set; the price is based upon the device being a "specialty item" in a marketplace generally *willing* to pay. > I've added up the cost of the obvious components > (headset, tone pad, aligator clips, batteries, isolation transformer) > and arrive at about $50. Ain't no batteries in a conventional telephone test set. From a circuit standpoint it is nothing more than a regular telephone with (today) switchable tone-pulse dial and a monitor-talk switch. In the monitor position, the set is little more than the receiver element in series with say, a .1 to .22 uF capacitor. Some sets have a polarity indicator - big deal, an LED along with one or two resistors, and possibly a zener diode. > The only thing I don't know about is the > monitor option, which is what I use most to debug the modems. What > makes up this circuit? Traditionally, nothing more than a receiver element in series with a capacitor. A better approach for data work is to use a higher impedance connection made by an externally-powered amplifier bridging to say, a 100,000 impedance. However, only one or two handheld telephone line test sets have such a battery-powered amplifier. > One final thing, does anyone know if I can use the telephone > isolation transformer on an old 300 baud modem to shave a couple > dollars? We've got some 300 baud modems around collecting dust. You don't need an isolation transformer for this application. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {boulder|decvax|rutgers|watmath}!acsu.buffalo.edu!kitty!larry <> TEL 716/688-1231 || 716/773-1700 {utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 || 716/773-2488 "Have you hugged your cat today?"
root@argus.UUCP (Kenneth Ng) (04/12/90)
In article <1990Apr10.142252.21706@sctc.com>, bies@sctc.com (Marty Bies) writes:
: Considering that you have $50 in parts. I would think that the time
: it would take to build and debug the whole thing and make it reasonable
: to use would far exceed the $200 cost of a new test set.
That might be if I were to purchase the components new. However, a fair
amount of the materials can be scravanged from old projects here. Furthermore,
I don't need components like the keypad because all I do is monitor the
presense/absence of modem signals. Lastly, I've always wanted to find out
how these beasts work.
: But then, my budget is like a bottom-less pit :)
Let's put it this way, I can't even purchase rj11 connectors.