The Double Current Interface

[M1ECY]

Hello Fred,

I used the following for the first test

itlx_TW39plus Beta 566


Then reprogrammed with

itlx_Doppelstrom-EN Beta 566

This is the currently installed firmware.

Thanks
Sean

[FredSonnenrein]

Okay i will compare the programmed sequences.

Our newbi Bambi from Australia is happy with that firmware.
Does the Problem occur in any case who presses the Clear button? (you vs. the opposite station)?

Can you check what‘s happening on the line when you press the clear button?

Best regards and a happy new year!

Fred

[M1ECY]

Hi Fred,

Only on remote clear - If I clear locally the machine shuts down as expected.

I will install some metering on the line to see what happens - May be a delay on response, back to work in the morning

[FredSonnenrein]

Hi Sean,

the sequence after remote clear is as follows:

a) the remote station clears, therefore the "receive" line of the local station changes to constant space polarity.
b) the local station (i-Telex) itself also switches to constant space (in the "send" line) and waits at least 1 second.
c) if the remote station switches (for any reason) to mark again, the 1 second timer ist reset to 0.
d) if c) does not happen, after 1 second (see b) the local station goes "finally" to idle state (yellow resp. green LED off) and reduces the current on the "send" line to a few milliamps ("weak space").

Can you compare this behaviour with your observations (with installed Doppelstrom firmware)?

In contrast to the sequence above, the TW39 firmware changes in step b) immediately to "weak space".

I hope this helps to find a solution.

For the dialling problem i will provide an test (beta) version soon.

Fred

[M1ECY]

Hello Fred,

Yes, I can try this but sadly not until the weekend - I will make this an important item for Saturday.

Thanks for your help

[M1ECY]

Well, several Saturdays later.....

The "Two Handed Dialling" problem is fixed... Must trust the developer, for he knows everything..... Increased the timing of the "Dial Pulse" from 5/100 to 20/100. This problem was entirely of my making, but possibly important knowledge for others - this pulse holds the UK control unit in dial mode - too short, and the relay for the dialling contacts does not remain energised.

I have a couple of hours spare time to look at the other matter of machine not clearing - first check will be line current at "weak space" hopefully as Fred suggested, just a resistor change.

Hopefully fully operational later today.

[M1ECY]

So an update for Fred.

Some measurements from the system

Machine at rest +20ma
Dial Button pressed, but no active connection -50ma
Connected, and receiving +/- 21ma
Connected, Idle -9ma
Call cleared by remote connection -32ma
Local Clear initiated +13ma
Machine Rests +20ma


I tried another test with the TW39plus firmware for comparison, though no measurements taken.

The dialling returns to two hand operation, which is probably right.

Remote clearing of the connection then works perfectly, so I think there is possibly something odd happening in the coding for the clear connection state, perhaps this was inverted upon early testing of the doppelstrom FW?

So, to summarise, the Doppelstrom FW works fine for dialling out, making connections and clearing down the connection locally, but remote disconnection of the call results in the machine racing, due to the incorrect signal state being sent.

The TW39 FW is almost fully functional except for the dialling out, where a two handed operation has to happen.

Hopefully this information helps find the cause of the problem?

I will leave the machine active on TW39 FW for now, this way the machine will automatically shut down after an incoming call

[M1ECY]

Additional information regarding the 2.2k line current resistor.

This resistor overheats dramatically in extended operation - I am now trialling a 3.6k 5W component - this has set the line current to the values I checked above

[Zaphod]

Is there now a double current interface that is available to buy as a kit?

[DF3OE]

Yes, the interface works as I would say.
I have a Sagem TX20 Australianized with a double current interface board that I got from Richard in Australia. It works perfectly.
Just ask Sean, he is our Beta-tester in the UK.