[Asterisk-Users] Do I need a ring capacitor to use TDM400P cards in UK

[David John Walsh]

Angus

a "BT" socket with a capacitor in is commonly refered to as a "Master
socket", and are very cheap even without wholesale.  It gets its name
from being the socket that BT installed into the house for the line,
all other sockets in the house will be slave or secondary (ie no
capacitor) (and its against the law to play with the one BT installed
- but thats off topic!)

I'm not going to name names of where you can buy them, but they
extreamly widely availible across the UK.

Its all from historic reasons from when BT started providing wall
sockets, and the phrase BABT aproved was common, quite a quirky thing
to the UK these days.

If you want exact suppliers, email me directly.

On 08/06/05, Henry Coleman <henry.coleman at voip-pbx.ca> wrote:
> Hi Angus,
> If you connect the phone directly to the outside line will it ring ?
> The ring from the C.O. provides a  >90volt AC (30cps) and is capable of
> ringing a standard phone ( a real two tone gong bell)  My guess is that
> the TDM400 card does not supply enough current to actually do this. Most
> modern phones have an electronic ringer which requires a fraction of the
> power and will work fine.
> 
> I don't quite understand the reference to a capacitor unless your phone
> is as old as I am  in which case the phone has 2 x pairs of  wires going
> to the phone plug. The first pair of wires are the "voice pair" and the
> second pair are connected to the "ringer" if this is the case  your
> phone will  work normally but simply doesn't ring.
> The fix is to connect two capacitors approx  *0.15 uf  250vw *from each
> wire of the voice pair to each wire of the ring pair  (you can do this
> inside the phone jack)
> This should not cost much (about a dollar) and can be found in any
> electronics component shop (try Maplin electronics) . Concidering the
> time and effort you might want to buy a new phone.
> 
>                                      0.1uf
> Wall Jack
>  TDM400                  | ---||-----------yellow-------0
> 0-----------green------0-------------------------------0
> 0-----------red---------0------------------------------- 0
>                                   | ---||-----------black---------0
>                                      0.1uf
> 
> Hope this helps ...Henry
>   * *
> 
> 
> Angus Comber wrote:
> 
> > Hello
> >
> > I have played about with a TDM400 card and plugged in some standard
> > analog phones.  I am using the card in FXS mode - for analog
> > extensions.  I did notice that one of my phones did not ring and I
> > wondered why.  I later read in Paul Mahler's book VoIP Telephony with
> > Asterisk that in his section on the TDM400 on page 127 he says "In the
> > UK, you may need an adapter that provides a ring capacitor, or the
> > phone may not ring."
> >
> > Can anyone confirm this.  Also what is one of those and where would I
> > find a good supplier?  I am in the trade so wholesale would be OK.
> >
> > Angus Comber
> >
> >
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