TDA & TDE sidetone problems?

[Phoneguy65]

Anyone here experiencing harsh and erratic bursts of sidetone volume? Particularly on lower frequencies?

It happens on the 30, 100, 200 and 600 and mostly with the 76xx series phones. If I use a 74xx set it's not perfect, but it's a lot better. I've gone into the MPU and lowered the TX settings on the DLC and even tried different settings on the LCOT audio levels but I still can't make the audio problem go away.

Anyone else have any wisdom to share on this problem?

Thanks!
Pat

 

[cwc3]

what does the help desk have to say about it?
have you got the latest rev's loaded on all the dlc cards?

 

[Phoneguy65]

The help desk has no fix, the MPR engineering setting adjustments ease the problem slightly, but by no means does it fix it.

We routinely upgrade the LPR releases of all cards to the latest release issued by the factory, either at the same tine we're out replacing cards for upgraded fuses, or on site for other routine MAC or service work, but this does not (and has never been suggested to) fix the sidetone problem. We don't come on site simply to upgrade card LPR releases unless there was a specific reason to do so.

Have you ever experienced this first hand? It's hard to miss on the 76xx sets. The audio is much better on 74xx sets and I've also noticed if you take a handset from a 74/72xx set and put it on the 76xx set, the audio is much better. This is clearly not a fix simply because they are shaped differently, but for a test, it's immediately obvious the sound quality & stability of the sidetone is better when using the older style handset. Take a 7630 and a 7433 and try them out on an CO call using an analog trunk. Speak normally and listen for pops and surges in the sidetone volume. A good test phrase for me is "How are you doing?" The "how" and the "Do" in doing tend to be very much louder than the rest of the phrase. This is just one example. In typical conversations we find the sidetone popping gets distracting and in extreme situations can sometimes give you an earache or listening fatigue. Also, it tends to be more specific to lower pitched (male) voices. Soft speakers, especially female soft speakers may not hear anything out of the ordinary.

It may be useful to point out the handsets in the Canadian market are a different style than those in the US market. I'd like to assume they are electronically identical, but I've spoken to one dealer who said he tried a US style 7630 and found the sidetone irregularity to be less noticeable. Granted he only tried one phone and that's certainly not a large enough test quantity to declare a pattern.

Compare a 76xx set to a 74xx set on an analog trunk call and let me know if you notice a difference.

 

[TelecomAvatar]

Is this on a digital circuit? Did you intentionally turn on side tone? In the USA side tone comes default turned off. We have to enable it through the RS232 port. This may be an option for you if you are on a digital trunk.

 

[Phoneguy65]

Read the text above. I mention the trunks are analog, and it's happening everywhere. This is not a single site observation, every TDA with analog trunks I've ever tried has this happening to a varying degree.

Also, it does not matter whether it's a 0180 nor a 0181 nor the 3180 as on the TDA30.

It also does not matter what LPR release is running on the cards.

It's just a theory of mine, but it may have something to do with the impedance of the TDA trunk cards. Just about everywhere in North America, analog CO trunks have an impedance of 900 ohms, but elsewhere in the world it's mainly 600 ohms, and they have standardized on one trunk card for the world market. For example, if you connect a phone designed for the UK market (600 ohms) to a line here in North America, you'll find the sidetone is quite loud, yet take the same set to the UK and it works perfectly. A friend of mine works for BT and we've sent various models of sets back and forth.

Here's a real oddity: Most the single line sets I've sent to him from our market work perfectly over there, but most of their sets have a much louder sidetone when connected to trunks over here.