rar@bridge2.UUCP (02/26/85)
Several people responded to my request for information about TCL transceivers. In general the comments were favorable. I have included the pertinent ones for reading. Ease of installation versus cutting the cable, size and reliabilty seem to be the most liked features. If anyone has further commments please mail them to me. SUMMARIZED COMMENTS ......................................................................... We use mostly TCL tranceivers purchased from Xerox. We currently have them on two Xerox Dandelions, a VAX with Interlan controller, and a Sun. So far everything has been OK. The only problem has been caused by a Xerox installer used to Teflon coax, which needs a shim. A shim on PVC coax results in too-short penetration of the teeth in the cable clamp for reliable connection. Their nicest feature is installation in 5 minutes without taking down the net, and their low cost. With the old experimental Ethernet tranceivers, also made by TCL (I think), we had two failures in 6 or 7 unit-years. In one a splash of solder finally shorted out a diode causing intermittent failure, which was cured when I pried off the solder lump. The other developed a short somewhere in the power supply circuit and suffered massive meltdown--fusing the transformer and driving power transistors and heat-damaging the rest of the components. It took a day and a half to figure out why the the computer room smelled vaguely smokey... Darrel J. Van Buer, PhD System Development Corp. 2500 Colorado Ave Santa Monica, CA 90406 (213)820-4111 x5449 .......................................................................... We (NBI) are using TCL tranceivers on currently small network. We are using the recommended spacing and following the rules. The TCL tranceivers look rather crude (back of the garage quality). We have both Ethernet I type tranceivers and 802.3 tranceivers on the same network and are using a variety of controllers. The current configuration is (802.3 unless specified): 1 VAX with Interlan 1010 controller (Ethernet I xcvr) 1 Integrated Solutions 68010 system with Excelan controller 3 NBI IWS/TWS systems with our own controller The VAX acts as a gateway to a second LAN. There are also a number of other machines that talk on the network but aren't really there yet. Over the next few months the network will expand considerably. We haven't had any problems with the TCL tranceivers. They work with the three controllers (actually we've used a 4th) in use. The bad points are in how they look. I would also like to see a tap that is a little easier to use than the screw-in type that TCL uses. The new Interlan NT100 looks better and is easier to move around. Good features are that TCL does use an LED to indicate power. That is often an important feature. 3COM doesn't use one and it is sometimes hard to tell where a problem might be. Another nice thing about TCL is the size. The box is smaller than the others I've used. Doug McCallum NBI ............................................................................. We have been using 8 TCL 2010ECS transceivers for the last six months to connect CS/100s to our Ethernet. All other transceivers on the net are DEC H4000s. We have had no TCL transceiver fail electronically, but we have had several instances of unreliable mechanical connections to the coax. o The TCLs are more difficult to install properly than the H4000s. o The metal case is connected to the coax shield, so precautions must be taken to insure that it does not contact ground. o The TCL must be fixed mechanically such that the tap block is not stressed to insure reliable contact. I recommend the side mounted version (ECS) which makes is easier to strain-relieve the transceiver cable by tying it to the coax. When carefully installed, the TCLs work just fine. They're good transceivers, but the mechanics of the H4000 tap and its plastic case make it my first choice. Keith Gorlen ............................................................................ I have about 30 TCL transceivers on my CS Department Ethernet, mostly connecting Xerox 8014s to it. Haven't had any problems except for one bad set of threads on the clamp. I installed them at the recommended 2.5m spacing, on a near-500m teflon cable. I also use DEC H4000s, one Interlan, several 3Coms, and 3 DEC DELNIs on the same cable. Advantages: o compact. o Can be installed without cutting the cable (I would NOT buy 3com). o fairly cheap Disadvantages: o not acceptable in air plenums o Interlan and DEC xcvers are even easier to install o Ethernet I rather than Ethernet II/802.3 compatible. Most new equipment we expect to get is E II. Cornell University C.S., Ithaca NY ........................................................................... We are using 6 2010EB transceivers as supplied by Ungermann-Bass of Santa Clara, CA. We have had them since May 82 and have had no prob- lems with them whatsoever. They did change the "stinger" somewhere along the way -- originally it was a rigid pin that forced its way through the center insulation on the cable. Later models have a spring-loaded pin that requires a different coring tool to pre-drill a hole in the insulation. This presented only a temporary problem during installation. We have them connected to three Ungermann-Bass NIU-2A network interface units and three U-B NIU-150 units. Bob Hoffman, N3CVL Pitt Computer Science ................................................................. We were using about 18 TCL tranceivers on a network of 68000-based UNIX machines and a couple of LISP machines. Over the period of about a year, NONE of them failed. Then, last November, we merged with Visicorp and moved into a new site and for various reasons had to have a NEW Ethernet cable and new tranceivers installed at this new site before moving in. All we could get in such short notice, were Interlan tranceivers. Since then, the whole net has gone down about 3 times - usually due to (what seemed to be and was diagnosed as) bad Interlan tranceivers. I've talked with the people who laid the Ethernet cable & tranceivers - they said the Interlan tranceivers are much harder to connect to the cable. Other people who also have worked with networks a lot have also said TCL has the best tranceivers. ................................................................. We use many TCLs here at Rutgers connected to Xerox Dandylions, a VAX or two, and of course a bunch of Bridge Boxes (CS/100s). I guess you can say we tolerate them. We like the (older) version of the Interlan the best and have not tried the new version (NP100 or something). At least TCL got somes heads unwedged and got rid of that rigid pin and made the cable clamp a little wider. This was the major reason that gave us bad feelings about them in the first place. The problem with the old TCLs were that they were hard to get a good tap and once that was made, the least little bang pushed the pin off center again. I guess what I am trying to say is if you still ship the older version with boxes, STOP, and ship them back to TCL and get the newer versions (spring pin and wide clamp). We have had many problems with the old version and none with the new version. Again, we have not tried the new Interlan, but I heard some bad words so far. I guess that I will ask for one on evaluation and give it a try. Also, we have not used 3Com thus far because you have to break the cable, but I hear that they are coming out with a clamp-on very shortly. For DEC xcvrs, you have to play games and file down the pins for PVC (Belden 9880) coax, but they seem to work. ........................................................................... I have used TCL xcvr's for about 3 years. This amounts to about 30-40 on a single network, plus various smaller setups at computer shows. Only one ever died on me, all others seemed to work fine. These were connected to various multibus based ethernet controllers from Excelan, Interlan, 3Com and Intel. I used standard spacing on the cable and standard lengths of cables. Also, I used several 50M xcvr cable to connect to the TCL's, they too worked fine. Monte Pickard Counterpoint Computers ...................................................................... We use them, have about 10 in service, use them at the recommended spacing, and find them to be quite nice. They're very easy to install, which is the nicest part. We've only had one problem -- they seem to keep failing in one particular installation, which is under machine room floor, around a lot of high-current 60Hz power. I haven't tried to debug the exact failure, or even tried to put the "failed" xcvrs back into service elsewhere; we've replaced the problem connection with a longer cable to a DELNI. But all the others we've installed have worked well since day one. Cheers, chris ......................................................................... We have a couple TCL transceivers installed on our network. They work fine, though I don't think we will install any more. The casting which forms the clamp assembly lies at the same electrical potential as the coaxial cable sheath. Not normally a problem, unless your cable runs by lots of grounded objects, like the little wires that hold up suspended ceilings, electrical conduits, etc. The TCL transceivers are a minor pain to ensure that their clamp does not come in contact with a building ground. As everyone knows, multiple point grounds on Ethernets are bad news. Hence, we won't be installing any more TCL (or other vendor's) transcievers which have exposed surfaces which are electrically connected to the coax outer shield. Norm Seethoff Technical Computing John Fluke Mfg. Co., Inc. (206) 356-5054 ........................................................................... As has been mentioned by someone else, TCL transceivers are reasonably priced at about $230 each or ~$150 each for the multiport variety. When I buy cable, I usually buy from my local cable supplier like Anixter. Belden has been one of the leading manufacturers of Ethernet, but they recently put a quality hold on the coax because the innermost foil would bond with the dielectric, making it difficult to remove for transceiver installation. Berktec and others also make the coax. I usually pay 70 to 80 cents a foot for the stuff in 1000 foot rolls. We have about 150 transceivers installed on many networks with several miles of Ethernet coax; I tend to shop around. I would NEVER buy one of the transceivers that requires cutting the cable for installation. We never have any problems with the vampire taps. -- from the DMZ of Skip Addison The Office of Telecommunications and Networking Georgia Tech, Atlanta GA 30332 -- Robert Rogers Bridge Communications, Inc. Mtn. View, Calif (415) 969-4400