Specifications

6
between Tip and Ring of the line in the phone. The ‘half’ ringer
is just the capacitor part of the ringer. The half ringer is
actually a capacitor in series with a zener diode and a resistor
that resembles one half of a ‘normal’ mechanical ringer. This,
in the U.S., is a 0.47 micro Farad capacitor without the addition
of the inductor part of the circuit, hence the name ‘half’
ringer.
4.3 V
4.3 V
0.47uF 250V
15K Ohms
TIP
Ring
Half-ringers represent a load to DSL if you are at maximum distance the additional load may interfere with
DSL. Common practice for SDSL installation is to disable the half ringer in the NID. If the phone company
installs a POTS/DSL splitter for ADSL the half-ringer is built into the splitter after the POTS filter so the
effect is minimized.
This is only a concern if your signal is marginal. If you think the half-ringer is interfering with DSL try to
get the Telco to install a POTS/DSL splitter rather then use the self-install microfilters. When the splitter is
installed the half-ringer in the NID is disabled.
2.2.1.7 Inside Wiring
Inside wiring is the cause of many DSL problems. The FCC recently mandated telephone inside wiring be
installed using the homerun method with at least Cat3 twisted pair cable. This means in new construction
each phone outlet is run directly to a central wiring closet, usually in close proximity to the NID. The cable
itself is of higher quality then the 4-conductor IW (inside wire) historically used for phone wiring. Each
pair is twisted to minimize noise pickup.
DSL was designed to tolerate poor inside wiring. The easiest way to test inside wiring is to connect the
DSL modem directly to the NID. The test jack on the NID automatically disconnects inside wiring. If your
speed improves inside wiring is interfering with DSL. The simplest way to isolate the effect of bad inside
wiring is to use a POTS/DSL splitter instead of multiple microfilters.
2.2.1.8 Wireless Phones
Wireless phones may interfere with DSL. The frequencies used by the phones do not overlap however they
inject a substantial amount of noise into the phone line.
If you are experiencing problems disconnect all the phones and reconnect one at a time. Sometimes adding
additional microfilters at the offending phone will solve the problem.
2.3 Cable Modem
The cable TV industry is being very aggressive delivering high-speed data. Historically Cable TV was a
one-way medium. TV signals originate at the CATV office, called the headend, and are delivered to all
cable subscribers. Cable bandwidth is divided into channels. Each channel carries one TV station. Internet
service is very different. Instead of a one-way connection from the headend to many subscribers each PC
needs a point-to-point connection so it can both send and receive. As is the case with DSL the CATV