sundance-communications.com/forum Forums General General Telephone & Systems Information Inside the central office

Paul, maybe I missed something, what does the term STD refer to. Over here it usually refers to Sexually Transmitted Disease! I have a feeling that is NOT what STD means in the context you are using it in. John C.

Not to get off my original topic but... years ago, probably around 1993, I made a call on a pay phone. Talked to whoever I needed to talk to, when I went to hang up the phone I flashed the hook three or four times quickly, then hung up the handset. After I hung up about $1.25 in quarters came out of the coin return! Essentially got paid a dollar to make a phone call! I was never able to duplicate the event at another pay phone. Even went back to the same pay phone later with no luck a second time. Wasn't sure if by flashing the hook I had caused the phone to "think" it need to give me a substantial refund or if it was just a bunch of coins jammed in the mechanism.

How quiclky a topic drifts!

Ouch, Mike! My guess is that STD is similar to DDD (Direct Distance Dialing) here. That's a term from the early days when people could dial long distance calls without the assistance of an operator.

Notifier, there were probably four quarters being held in the phone's "escrow chamber" that got stuck. Coins are held there until the phone is signaled to keep or return the coins. Sometimes they get stuck and all it takes is the weight of a fifth quarter to break up the jam. Why you got any coins back was likely due to a polarity reversal on the line. This happens quite frequently with cable repairs in urban or suburban areas. The command to keep your coin was sent by the CO but with the polarity being reversed on the line, the phone was told to return your coin (and the others that were held in escrow during the cable repair).

There are all kinds of wacky stuff that could be done to trick pay phone circuits. That's probably why most of them are now "intelligent" phones. Hey, BellSouth got so tired of the BS associated with them that they stopped offering them quite a few years ago.

It sure isn't! My mistake for not explaining the terminology.

STD = Subscriber Trunk Dialing, which as Ed suggested, was the British equivalent of DDD. The term isn't used so much these days, but our area codes were once referred to as "STD codes."

I don't want to hijack the thread, but if anyone is interested in the history of the British system I'd be happy to discuss in a new thread.

One thing I forgot to mention on the payphones above though is that the post-pay boxes didn't use tones to signal coin deposits back to the C.O. but instead operated interrupter contacts to send a train of pulses back, very similar to dial pulsing except that the contacts had a 5K resistor in parallel. The mehcanism was completely mechanically operated, hence the need to push a coin in quite hard. You'd actually hear the mechanism whirring for a couple of seconds afterward as the pulses were sent out. The lock on the coin slots was operated simply by line polarity, since it was normal at that time for battery to be reversed right back to the calling line when the called subscriber answered.

In the old SxS (step by step) the coin control circuits had an option, the central office could option the time between answer and collect. We had ours set at 45 secs. If you could talk within the 45 sec after ur party answered and hang up, you would get ur coins back. IF you talked longer then 45 secs, you paid.

The sound that indicated the deposit of a quarter was called a "bong" not a "dong."

The coin collect polarity is + 130Vdc across both T & R to ground, and the coin return polarity is - 130Vdc across both T & R to ground.

Positive polarity = money for Ma Bell. Negative polarity = no money.

Ah, that makes it easy to remember!

Here are a couple of scans to illustrate the old G.P.O. A/B coinboxes that I described above:





In the schematic:

Contacts CB1 operate upon the insertion of the first coin. CB2 operates when the correct weight of coins is detected (two pennies at one time!). Both CB1 and CB2 restore to normal when either the "A" (collect) or the "B" (return) buttons are pressed. The "B" button also operates the CB3 contacts via the clockwork timer. D9/0 are the special dial contacts which allow an operator (0) or emergency (999) call to be placed without coins.