But first : You have to bear in mind that System X is just a generic term for a whole load of different switches from loads of different manafacturers including Bell Laboratories (5AESS), GEC Plessey Telecom (TXE) Erriccson (AXE10) and British Telecom (Smaller Concentrators, MUX's + various other shit).

Anyway, I'll try to answer in relation to what I already know, so dont be surprised if some of what I drool on about is partially or maybe even fully wrong.

Question one : The editor for use via the ISDX Terminals

I wasnt aware of the actual name of the terminals used, and I always thought that ISDX was a simple PBX/Caller Handler system. We have an ISDX unit installed in my local probation office, so I'll take a closer look next time I'm dragged in there...

However, as you seem particularly engrossed in the AXE10 in particular, The name of the Interface and Editor is FIOL. It is simply referred to as the FIOL interface, and I cant remember exactly what FIOL stands for. Any other questions regarding interfacing? Its such a wide topic that you could write a book on it.

Question Two : Other ways to talk to System X

As in Terminal wise, or simply testing or other facilities like REMOB's? Theres the 174/5/6 tests, and there is usually a gamut of other test numbers specific to each exchange, for individual testing and evaluation. As for programming via a keypad, well, wouldnt we ALL love to know how to do this? Im afraid I havent seen any paperwork referring to DTMF prognosis and programming, but I'll keep scanning those patents and trashing those bins...

Question Three : How do you dial in?

 Well, I dont work for BT, Contrary to Popular Belief and much to my personal chagrin, so I cant really take it from that angle. I could quiz some engineers, but I prefer not to mix with the enemy. The switch can be accessed externally via the Operator SubSystem Dial-in, a fatal flaw in the System X's otherwise impenetrable armour. This will then allow you to control all customer switching and routing, and perform ALL the usual operator thingies you can do, including: 
        Providing Directory Enquiries
        Tracing calls
        Placing Trunk calls
        Re-allocating Numbers
        Blah, Blah, Blah

Basically, it provides you with all the power of a full external operator, regardless of where you call in from. Sound like fun? Yeah, but just try and find the frigging dial-up, esp. if you live in an area served by a mucho large exchange. Also bear in mind that even when you connect (Its 2400, 8N1, No protocol, by the way) It will just sit there waiting for a specific wake up string. I'm still working on this, and have been since I first trashed my local switch.

Question four : Monitoring

Hmmm. That sounds like an interesting method, but a little bit to complicated. The way I've seen it done (I SWEAR to SATAN, I DONT work for British Telecom!) is to access the MMI (Man Machine Interface, or : Terminal. Doh.) and to issue the local test access command. You then set up a speech path, enter the access group of the number, its last six digits (Its only a local test) and then enter either its equipment number or directory number. This will allow you to monitor all the stuff you never hear on a normal call, like Equal Access codes, MF tones, blah, blah, as well as the conversation. Very boring. You've heard one, you've heard em all.

If you want more info on call monitoring or listening, then download the file entitled "Its your line to the phone tappers". It details how a line was tapped at the MDF in the old exchanges, and how it is now routed to the listening station Next to Victoria Station in London, via a few simple MMI commands.