Touch Tone Charges - Bell Canada Still Charges Extra $2.80 a month [Telecom]

For many years Ma Bell used to just reverse the line polarity so Touch Tone dials wouldn't work. Of course if you knew about this you simply [flipped] the pair at the demarc.

The Touch-Tone pads on WECO instruments could be disabled by reversing tip and ring, but those of other manufacturers didn't seem to care. Does anyone know why this was so? Was WECO's Touch-Tone pad designed for it, or was that a by product that became a feature?

There is considerable suspicion that no such "pulse to DTMF" converter exists. A telephone switch must respond to DC signals (pulses) because the hookswitch sends DC, so responding to DC pulses (such as a subscriber flashing) is an integral part of the switch function. Touch Tones are not digital, and must be converted into a form the switch computer understands. Accordingly, there is no evidence that pulse costs more. There's a separate ongoing long discussion in this newsgroup on this issue you may wish to review. If you have technical literature describing the "pulse to Touch Tone converter", could you cite the book?

I do not think any "filter" is added to the line. Rather, the switch software merely ignores Touch Tone signals from that subscriber. It's no different than if you attempt to flash to get 3-way calling but your line is not equipped for that, when you flash, nothing happens.

It was a consequence of that extra-special pad design. It saved money by having only one of those expensive transistors.

True, it had two tapped cup-core inductors, and was hand tuned; but we all know transistors are expensive!

The odd thing with WECO pads was that the inductors had a tap for the fourth column tones that were usually used only on AUTOVAN phones: the fourth column on those pads was for the military precedence levels. Since the tap was there already, many hams used it to add a column to their pads, which they needed for control of ham repeater stations.

Bill, W1AC

Actually the single transistor was a brillian design, it acts as a simple amplifier and then uses an LC tank to generate the frequencies, hence the two cup core inductors.

A recollection, perhaps an incorrect one: In the early days (Ernestine Days) of Touch-Tone, Ma Bell didn't want you to be able to send out tones once answer supervision was present. Does this click with anyone?

I don't know if it was a feature WECO produced sets. But the initial Touch Tone sets most definitely had thier T/R swapped. If a Bell installer was putting one in a home he'd swap the incoming pair.

Later sets dropped the polarity guard entirely since they were going to be sold directly to customers.

In the NYC area at least, as late as 1980 or so (I didn't use this later) a "toll call" would cause a current reversal as the connection was being processed. So.... if you placed a diode in series with the phone line, the person could make "local" calls but no long distance (that is, they'd get disconnected).

Incidentally, I discovered this when perusing the newspapers and coming across one of those telco teensy print legal notices. I don't recall the exact wording but it used the term "battery reversal" (or maybe "battery current reversal") for a tariff regarding toll blocking. It also stated that the telco wouldn't be liable if the caller still got through..

Oh, and for a[n] historically interesting advert of this sort, check out a scan I made nearly 2 decades ago:

According to both an AE catalog and a Bell text, it was standard practice for a Step by Step swtich to reverse polarity after the call went through.

For semi-post-pay public ph>A recollection, perhaps an incorrect one: In the early days (Ernestine

I doubt that's correct. We had Touch Tone in that era and it would send tones during the course of the phone (which the other party did not appreciate since they were loud).

Touch Tone sounds were very carefully chosen to avoid sounding like human tones or other internal system tones that they could be confused with.

But very early on Bell pushed the idea of connecting to computers via TT phones. In those days our bank staff used a TT pad to contact their computer. (It was a separate pad since the neighborhood itself hadn't gone TT yet so the phone still had a dial on it.)

Reversal on supervision was a function of the CO. As I recall, most step-offices did, but XB did not. I don't recall about panel.

Of course coil phone lines DID reverse...

To meet the very high service demands of the Bell System---which is why 40 year old units still work perfectly fine today--they used very high grade components. As they put it, the phone had to withstand drops to a hard floor, a cold storage locker, and a hot humid sunny window sill.

Further, 40 years ago high grade transistors were not cheap. Now whether it was necessary to use such high-grade durable components is tough to say. But since the Bell System owned the equipment and was responsible for all maintenance, it was to their advantage to reduce downtime and maximize the life of the equipment.

Yep - I had an old red 2500 set with a toggle switch. Flipping it would toggle the rightmost column from 3,6,7,# to the F, FO, P etc. frequencies.

It was a brilliant design only when the transistor cost a few bucks, and the magnetics didn't.

But a few years later it was 180 degrees around. But Ma/WECO kept making the same pad for about 20 years....

Many newer WECo telsets or pads had a "Polarity Guard" which was basically a full-wave (bridge) rectifier.

Line polarity had become a big problem after Divestiture. Many people were purchasing their phones at their local Five & Dime or drug store. These were designed to work on unknown polarity because so many homes were actually wired reversed.

Sadly, some employees were not as well trained as those from yesteryear, and their supervisors also couldn't care less.

Here's a good site with telset wiring diagrams:

The old ITT Telecommunications / Cortelco 2554 I had had a tone pad with a Mostek IC on board to generate the tones using a "colorful" 3.58 MHz crystal, the same crystal used in NTSC color television sets for chroma processing.

I can't remember the date code, but it seemed to be in the early '70s or so.

I presume some of the Independents felt it would be better to use one IC than to have to tune coils in a tone-dial phone.

I ran into this "feature" back in 1998. I was at a payphone at the garage at Hoover Dam on the Nevada-Arizona border. I tried to use an

Not totally. They did make evolutionary changes "under the hood". The 500 set was improved in numerous ways between its introduction and termination. As mentioned, dial lamps were converted to LEDs from plain bulbs.