[VoIP] Oslo phone

[Steph Kerman]

Perhaps it just has a low impedance ringer that causes false trip 
because of inadequate design of the channel card. 

If there is leakage you will be able to see that by placing a DMM set to 
DC mA in series during ringing.  The DMM should register zero during the 
silent intervals.  In theory it should register zero during the ringing 
intervals too but some DMMs do not behave well below 60 Hz so it may 
thrash around, which would be a false indication.  If it registers zero 
during ringing that would be a reliable indication that there is no 
leakage problem.

Most likely if it does have too low an impedance for the channel bank 
you can put a resistor equal to the DC resistance of the ringer in 
series with it and it will still ring adequately without tripping 
ringing.  What is the resistance of the ringer coil and the series 
capacitance value? 

What model Oslo phone is it?  There are modern ones and very antique 
ones such as were used on the first WECo Rotary offices.  These have the 
7001 type dial with 0 and 1 holes at the bottom and a number plate which 
rotates with the finger wheel.

Steph

Russ Price wrote:
> I recently found an Oslo phone on eBay (one that was in a bit better 
> shape than the one in Ian's post).  The good news: when I use it on the 
> channel bank with the dial pulse mapping option, it dials correctly. The 
> bad news: When I ring the phone on the channel bank, it will ring a 
> random number of times, and then suddenly Zaptel will think that the 
> phone was answered, just for it to immediately go back on-hook.
>
> If I connect it to my TDM400P, this problem doesn't occur.  However, the 
> dial is slightly too fast (shades of my North Electric set), and it 
> doesn't dial accurately on the TDM400P, pulse mapping or no.
>
> The ring problem also doesn't occur when the phone is directly connected 
> to the CO, or even, surprisingly enough, the Panasonic switch.
>
> When I open the phone up, I don't see any obviously bad insulation, but 
> the wiring is all bundled up, and most of the internal wiring is 
> *soldered* to the terminal strip.  I can't disconnect the ringer without 
> unsoldering or cutting wires.
>
> My prime suspect is the capacitor, but still it rings just fine without 
> glitching on anything except the channel bank, and it doesn't matter 
> which port I use on the channel bank, either.
>
> At this point, my options are: regulate the dial speed and use it on the 
> TDM400P, use it as outgoing-only on the channel bank, or try to figure 
> out what's going wrong.
>
>