Seeing as how charging starts upon b-answer it's unlikely, unless they consider the through-connection of the voice message telling you that the number is non-existant as the b-answer. If so, I agree that this is wrong.
CCITT [now ITU] E.231 recommends that no charge should be made for calls which terminate on services for suspended, cancelled or transferred subscribers. However, there is also E.124, which is entitled "Discouragement of frivolous international calling to unassigned or vacant numbers answered by recorded announcements without charge". This recommends that the provisions of E.231 may be suspended if it is determined that calls to specific out of service numbers are "predominantly frivolous."
This situation often occurs with the Cellular networks. As things stand right now, only calls that are answered get charged. Calls that get engaged or ring tones ONLY are not charged.
Exception: calls that route to a mobile network (or to a direct-dialling-in PABX) and THEN divert to an external number, are charged from the moment the diversion takes place, even if the diverted leg of the call fails to connect (for whatever reason).
But, in the context, answered can mean "answered by the mobile network on behalf of the called party". Of course we all know that phrase is a con, but BT insisted on the Cellular networks agreeing to do this, before they would allow them to interconnect with the BT network. Mercury followed suit!
A cellular network answers calls on behalf of the called party (and plays that annoying announcement) when either: (a) it can't get a response from the called telephone (even if this is solely due to congestion in its own network) or (b) the telephone is rung for 45 seconds without a reply.
(pence per minute approx. These are the costs to the holder of the line.)
Peak Standard Off-Peak
0345 13 10 7
(+cost to caller 4.4 3.2 1)
0800 16 12 9
Try also contacting British Airways Speedwing who are reselling their bulk
purchased time for these services on to other potential users. They are
offering between 17-20% discounts depending on usage. The sevice is
called SpeedLine and sounds curious only in so much as the only thing you
seem to get from SpeedLine is an order/service. BT do everything else
including billing you.
Call Speedwing on (0181) 564 1000; Peter Jones is on (0181) 564 1489.
[info given by Alan Jay - alanj@ibmpcug.co.uk, 14 feb 94]
[See seperate postings, <URL:http://www.pobox.com/%7Etis/>, or contact your telephone provider]
[from julian@bongo.tele.com]
The average bill with "Unlimited local calling" in Pacific Bell territory is $13-14 per month. Of course Long Distance increases that. I have some lines that are used for local calls only - two modem lines - They are busy about 16 hours per day each. I pay $13 and change per month for each line The average U.S. residential line is used 20 minutes per day.
[from julian@bongo.tele.com]
Also note that 'local' in the US often means 'own exchange', whereas for BT is is charging-group related, which usually means all the exchanges in your local area.
In the U.S., most phone companies have several "tarrifs" or rates. For example in Pacific Bell Southern California. You can get "measured service" which means local calls are charged at $0.10 per min. Or variations of the above, say so many free local calls, and any above that number are measured.
You can also get "unlimited local calling". For a fixed fee, you get all the local calls you want. The "local calling area" is usually a 8 -16 mile radius. Unlimited local calls for residential use costs me about $14.00 per month. Long distance calls are extra.
So unless "own exchange" is a rural one with dispersed subscribers local calling areas encompass up to hundreds of exchanges as is the case in the Los Angeles area.
[For comparison, $14.00 is about UKP9, or about UKP27 per quarter, against BT's quarterly rental of UKP25 (or very close, at 17/04/1995, + VAT). ]
In a GPO Strowger exchange this situation was handled by splitting a unit into 10 part-units. At changeover, therefore, you'd be over/undercharged by no more than 10%.
With a crossbar, the "undercharge" was specified by PO/BT as an exchange facility (on the basis that a call must never be overcharged). The difference between Strowger and later systems was that timing of the subsequent periods proceeded in units of 10/10ths of nominal time whereas Strowger always gave 11/10ths on subsequent units (and between 10 and 11/10ths on initial).
This was emulated by digital exchanges. Some old crossbar exchanges would charge the call at the original rate. With universal per-second charging, this is no longer the case.