Thanks to all respondents on my earlier home networking thread. Just one or two more points if I may....
Thoughts are:
Fit Clarity Adaptor #16134 at master box. As I have 2 cables run to loft already, use one cable to take 2, 3 and 5 upto loft and connect to existing distribution juntion box for telephones. Use separate cable to take A and B to loft.
Is there an "ADSL only" connection box available that I can terminate A and B in (in the loft) for the router/modem - RJ11?
Is the base plate for the master box different between analogue and ADSL? From the web picture of the #16134 it appears to have a similar male part to plug into the base plate.
On Thu, 18 Jan 2007 13:50:33 -0000 someone who may be "TheScullster" wrote this:-
Something you didn't bother to tell us earlier, when you gave the strong impression that there is only one cable.
You can use an RJ11 or RJ45 socket. The lead will be an RJ11, but this will plug into an RJ45. See the bottom of
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Is the base plate for the master box different between analogue and ADSL? What you do is unscrew the existing bottom bit at the front and put the new one
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in. If you have an older NTE5 get the screws for 20p and you won't knacker the threads, so you can put the old bottom bit back should you want.
The new bit sticks out a little and so may not find favour with the domestic authorities. Tell her that it is a lot neater looking than dangly filters everywhere.
How do you know which connections to make off the A & B feeds to with these modules? I have fitted the RJ45s for the wired network, but ISTR these were just colour coded for network wiring colours!
B leg should be -48v, but I don't suppose it matters really, even for most phones they doesn't care, you can get polarity reversals with caller ID anyway, and when you've passed through a microfilter it should chop off DC up to 3KHz or so, as the ADSL signal is above that frequency.
Colours depend if you're using EIA 568A or 568B, so long as you use the same each end you should be OK, unless you using gigabit (or the uncommon 100 base-TX) you only need 1/3 and 2/6 pairs anyway.
But will the standard telephone extension wiring still operate, provided I connect to 2, 3 and 5 of the new ADSL faceplate even with the old non-ADSL service still running?
yep, the filter lets through signals from the incoming pair within the normal phone frequency range to your phone wiring, until you have ADSL service that's all that will be on the line anyway.
An unfiltered signal direct from the A/B legs goes to the router, it internally filters out the bits it's not interested in. I realise this is slightly at odds with what I said earlier, the DC->3KHz signal is what is allowed through to the phone side, rather than what is blocked from the ADSL side.
Would also recommend fitting an in-line surge protector also from Clarity
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be fitted as near as possible to the incoming ADSL filter..
I once lost all our phones which are daisy chained (like you describe yours are) plus a PC modem in a lightning storm. cheap (=A313.98) for the protection it offers.
This type of surge protector is completely useless for protecting equipment which is connected to anything else against lightning. You need common mode protection, which will have a grounding connection point on the surge protector.
Interesting...It would be highly useful to know what protection (or specific pretective device) you would recommend for the type of separated ADSL/PSTN home network discussed in this thread. How should the protected circuit be configured?
For the reasons given, IMHE some protection is absolutely essential.
Are you saying that it is the connection to the PC & router which makes the Clarity device is ineffective? Not entirely sure that I follow why. What circuit arrangements will the Clarity device protect?
The only information I have is the very brief description on the Clarity website, but the device appears to be a gas discharge tube which shorts the incoming telephone line on oevr-voltage. So long as there isn't a parallel fault on the local power supply and the local ground plane potential stays unaffected, why isn't that enough?
Clarity makes a connection between two wires. Let's say a surge is 'pushed' down A wire while B wire 'sucks' that surge. Therefore a Gas Discharge Tube (GDT) shunts that surge from A to B; does not pass through modem.
However that is not the type of surge that typically does damage. Destructive surges, that seek earth ground, 'push' down both A and B wires. Now that surge is on both sides of the GDT. GDT sees no voltage (shunts nothing) as the surge continues down both wires, through modem, and into earth. Protector sees no surge as modem is destroyed by that surge. Andrew describes it:
In North America, these earthed 'whole house' protectors are installed, for free, on every subscriber line where it enters a building. Protectors don't stop or absorb what 4 kilometers of sky could not. Protectors shunt (clamp, connect, divert) that surge to earth. A surge earthed where it enters a building will not overwhelm protection already inside the modem.
This is also how BT does it. Their $multi-million computer connects to overhead wires everywhere in town. Does BT shutdown phone service for every thunderstorm? Do operators remove headsets so as to not be shocked by lightning? Of course not. BT even before WWII was earthing every wire that entered the facility. A surge that is connected to earth will not go farther inside a building to overwhelm protection at computer or operator.
Clarity device does not do this. The Clarity device is not designed to earth common mode transients. How do you know? Where is the less than 3 meter dedicated connection to earthing?
Some telephone line protectors:
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Unfortunately, some of these POTS (Plain Old Telephone Sevice) devices may have too much capacitance for RF frequencies in ADSL. Remember, ADSL is radio frequencies. A filter that would stop or block surges would also block ADSL signals. And a shunt mode filter with too much capacitance would short circuit (leak) too much ADSL signal to earth. Extra care is required for a low capacitance protector that is also rated for higher frequencies - for ADSL.
One of those manufacturers states an important characteristic of effective phone line protectors:
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This is accomplished by using a ground wire no longer than
That earthing wire is about 2 mm and less than 3 meters because a shorter distance to earth means better earthing. A common mode surge earthed before it can enter a building should not seek earth, destructively, via household appliances. As Andrew noted, destructive surges are common mode; seek earth ground; require a connection to a building's single point earth ground.
It's both... The broadband splitter's filter prevents the broadband part of the incoming signals from entering the telephone-type equipment, since they aren't designed to provide a matched termination at such high frequencies. Without the match, it is likely some of the incoming broadband signal's HF energy will get reflected back into the phone lines to be seen as as noise.
The filter also prevents any HF noise picked up or generated by the telephone equipment *and associated house telephone wiring* from getting injected onto the phone lines, again to be seen as noise.
The ADSL modem also has a filter, but of the opposite type. This is to stop the low frequency telephone signals and the associated LF noise, such as mains hum, from being seen by the ADSL modem circuits. You don't normally see this since it is part of the modem design. This is why the splitters only filter the telephone side and pass the DSL side straight through.
Note that the pick-up of noise on internal house wiring, from sources such as fluorescent fittings, thermostats, pin-3 ring signal, etc., is why the preferred installation is to use a faceplate or similar splitter mounted as close as possible to the incoming wires, as mentioned in other posts. This gets the DSL and the telephone signals separated as soon as possible so the DSL part can be carried to the modem without being subject to any additional local noise sources.
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