atcomsystems.ca/forum Forums General General Telephone & Systems Information reverse polarity

SLC-96s are polarity sensitive when transporting individual POTS across fiber. If the polarity is reversed at the CO side connection, the field side of the SLC96 circuit will still provide dialtone and the ability to successfully place calls, however no ringing current is received for any inbound calls.

Cronos Machine,
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A little off the topic perhaps, but what was used over a carrier system with the old SF trunk signaling there?

Was it simply removal of the reverse-direction 2600 or 3700Hz for more than a certain length of time which signaled the CAMA equipment to start charging?

Picture one boy, aged about 13, "playing around" with the local phone system. Given the polarity reversal for any chargeable call here, a diode inserted in series with the phone worked wonders!

And the term "phone phreak" was born!

Then they found out about the A-B-C-D dial pad buttons, stated playing with balloons to make weird noises, tin whistles, ad naseum! Let's see, wasn't the term Blue Box indicative of a device to beat toll restriction, by putting out some string of tones or something? I guess I should be glad I didn't have any toll calls to people that I liked to talk to. I'd probably still be in jail!
John C. (Not Garand)

The ABCD buttons, which translated to

A (697/1633, FO): Flash Override
B (770/1633, F): Flash
C (852/1633, I): Immediate
D (941/1633, P): Priority

would not have helped make a toll call free. The tones required to do that ("MF") were not ever placed into the hands of the subscribers. (and for good reason)

The blue box replicated the MF tones, which were 700, 900, 1100, 1300 and 1500 Hz.

Not forgetting 1700Hz for key-pulse and start.

Besides the "Blue Box" there was also a "Red Box" that produced the "cha-ching" sounds for the coin phones through a little speaker. You held it to the xmitter and off you went.

Also a "Black Box" that was only good if your line was on #5 X-Bar. It only worked for incoming calls, you would have someone call you collect and ask for George Washington (or similar). When you both hung up, you threw the switch on the box. When your friend called you back the CO never registered that the phone had been picked up and the calling party was never charged for the call.

There wasn't much to the box, as I recall. A couple of capacitors and maybe a diode or two.


The ABCD buttons were for the Autovon network only.

Sam

Free incoming calls (free to the caller, that is) were possible here under SxS by placing a suitably high resistance across the line.

It had to be low enough to trip the ringing after a couple of cycles, but high enough that it didn't provide sufficient D.C. current to operate the "called side" line relay in the final to return answer supervision. 10 to 20k or so worked on the average line (so I've been told, you understand . Having tripped the ringing, it was a case of providing local talk battery for the phone and coupling to the line with a capacitor or two.

On the coinphones, the old pre-pay boxes were ridiculously easy to make free local calls from for anyone who knew. All one had to do was not deposit any coins whatsoever and pulse out the required number using the hookswitch!

The post-pay boxes which came in during the 1960s were immune from that.

Reversal of Polarity equals a wink in wink start signaling... Could that be possibly what you’re wanting to know?

A little off the topic perhaps, but what was used over a carrier system with the old SF trunk signaling there?
Paul in the area that I covered (fairfield county Conn.) carrier was never used between the SXS and XBT. Carrier was between class 4 and above with the exception of ESS class 4/5