OBI100: Off-hook sometimes undetected using line powered speakerphone

Started by Zoltan, September 20, 2012, 10:16:08 AM

Previous topic - Next topic


I use a Uniden CEZ260 corded line-powered speakerphone. The phone uses 4 AA batteries to maintain caller-id history and power the electronics, but the batteries last for over a year, so for most of the power-hungry voice stuff it uses the power supplied by the line. The phone probably has a capacitor that charges up when the phone goes off-hook. If I press the on-hook button while still holding the phone to my ear, I can hear a faint click after about 5 seconds when the capacitor runs out of juice and the part of the phone that uses line power powers down. If I go off-hook immediately after that, I usually do not get a dial tone, and in the web interface I see that the phone status is On Hook, but despite that it sees loop current and voltages that normally correspond to an off-hook state. I see this in Port Status:

State: On Hook
LoopCurrent: 19 mA
VBAT: 17 V (12.1 V)
TipRingVoltage: 7 V

When it's really on hook I see:

State: On Hook
LoopCurrent: 0 mA
VBAT: 57 V (12.1 V)
TipRingVoltage: 45 V

I suspect there is some unusual current when I pick up the phone and the capacitor is charged which prevents the obi100 to detect the off-hook state. But this does not happen all the time, if the phone is on hook and idle for a while, then I have no problem when I pick up the phone, it only happens after I hang up and pick up again right after the line powered part of the phone powers off. And after that it takes about 10 seconds on hook to get back the dial tone.

I have no problem at all when I attach a plain cored AT&T 210 Trimline phone, I always get a dial tone there. This seems like an issue that could be fixed in the firmware. I hope that my speakerphone is not frying the obi.



Well, all the response from OBI support was that I should buy a new phone, not really a a fix. So instead I've decided to ditch the OBI stuff, buy a Cisco SPA112 device (basically the same price but supports 2 lines instead of just one), install Asterisk on my DD-WRT router, and now I have a working system far more flexible and powerful than OBI ever was. And of course the SPA112 has no problem with my phones.