My PSTN line is connected to my Obi110 LINE port, and incoming calls correctly are routed to my PHONE port. However, I've noticed that when the calling party hangs up, perhaps after leaving a voicemail message on my telephone's answering machine, it takes several seconds for the Obi to detect the disconnect and actually hang up. This results in several seconds of dead silence on the answering machine, or perhaps even a few seconds of dialtone. This does NOT occur if the PSTN line is connected directly to my telephone.
Is there a way to improve this on the Obi?
Thanks!
Possibly, but it varies from phone line to phone line. You'd have to go into Physical Interfaces, LINE Port, and try tweaking settings in the PSTN Disconnect Detection section.
It would help a lot if you could throw a voltmeter across your phone line and watch to see if the voltage or polarity changes when someone calls you and then hangs up (while you keep the phone off-hook). Typically, phone systems signal the end of a call one of four ways:
- Polarity Reversal — in this case you want to make sure that the DetectPolarityReversal setting is checked
- Momentary drop of all voltage/current on the line, known as "CPC" (Calling Party Control) — in this case you want to make sure DetectCPC is checked. If the CPC is VERY short you may have to reduce the value of the CPCTimeThreshold setting, but that would be quite unusual.
- Fast busy or some other tone — in this case you need to make sure that DetectDisconnectTone is checked AND that the frequencies and timings in the DisconnectTonePattern match what you're receiving. This one can be tricky, especially if you are outside the U.S.A. or Canada and you have no idea what the phone company is using for a disconnect tone. Note that if they are immediately sending a dial tone (which most phone companies don't anymore because it makes toll fraud too easy) then you'll definitely need to change the DisconnectTonePattern to match dial tone frequencies.
- Dead Silence - this is the hardest to reliably detect because it can also occur naturally during a call. There are three settings to deal with silence: DetectFarEndLongSilence, SilenceDetectSensitivity, and SilenceTimeThreshold.
Often you will get two or more of these things — it's not uncommon to have CPC AND a fast busy, for example. You should try to detect all such conditions if possible, except silence — I typically do enable silence detection but set it to something very long like 1800 (30 minutes) in order to release any calls stuck forever on hold. In your case, my guess would be that you are not getting polarity reversal, that you're getting either no CPC or a very short one, but that your phone company is sending you tones of some kind, however they just aren't the tones your OBi110 is looking for. OR — there is one other possibility you should be aware of.
It may be that your OBi110 is receiving the disconnect just fine, but is not sending what your phone/answering machine wants to see as a disconnect signal. In that case you'd want to go into Physical Interfaces, PHONE Port, and in the Calling Features section make sure that GenerateCPCSignal is enabled for both Inbound and Outbound calls. Then in the Tip-Ring Voltage Polarity section, try setting the IdlePolarity to Forward and the ConnectPolarity to Reverse (or vise versa, just so the two settings are different). Try that, and if it still doesn't work, then in the Timers section, try reducing the CPCDelayTime (try 1000 or 500) and increasing the CPCDuration (try 1000).
Hope this helps.
Wow, MichiganTelephone, what a terrific and thorough reply! You've given me a lot to work with, so thanks very much for that. I'll do some investigating over the next few days to see if I can narrow it down.
Thanks again for all of the details!