Last number readback 1471 (or *92#)
The current switches here use *27# for last-number readback, although that number has never been publicized. The 1471 code was mapped to *27# to allow non-DTMF users to access the service, and that's the only number which has ever been published. *28# (also unlisted) actually returns the call to that last number.
Most of other standardized codes (for this side of the Atlantic) are used in the usual formats, i.e.
*
xx# To turn on some service
-or-
*
xx*
xxxxxxxxxx# where extra information is needed.
#
xx# To turn off a service
*#
xx# To check the status of a service
Where
xx is:
55 Alarm service
56 Regular alarm service
21 Unconditional divert
61 Divert on no answer
67 Divert on busy
43 Call waiting contol
40 Charge advice (ringback with cost)
etc.
Loads more for call barring, incoming call blocking, etc.
There are several other codes which are programmed into the switches but are not publicized, e.g. *66* <number> # lets you set up both divert-no-answer and divert-on-busy in one go, and #66# lets you cancel both together, even if they were set up individually with *61 and *67.
There are also some variations between system X exchanges (installed from the early 1980s) and system Y/AXE10 (later) exchanges. For example, on system Y you can insert an extra parameter in a *61 string to set the delay in seconds before divert, whereas on system X it's fixed at about 15 to 20 seconds and can't be changed.
Conversely, on system X you can dial a kind of "master" status check code -- *#001# -- to get a readback of all services currently enabled. That's not available on system Y/AXE10.
