1967 Northern Electric 1500

[luns]

425E is a straight replacement for the 425B and is for rotary dial. I believe the only difference is the treatment of the C terminal (screw terminal instead of a soldered wire.

The 425 network for touch tone phones (I think it's 425J or K) have two additional terminals, T and S, and omit the capacitor for the dial switch snubber at terminal F.

425J omits the varistor equalization, while 425K adds T and S and omits the capacitor on F (there's no harm in having it, but I'm sure they were deleted to reduce cost). Both were listed for use with touch-tone, 

The above is all from 501-135-100, which described the current usage as of March '74, when the 4010 and 4228 networks were also in use. This doesn't rule out different usage earlier on though.

In fact, 502-510-450CA from Oct '71, shows a wiring diagram for the 1500D and others, with a 425E network in it, and just as Phonesrfun pointed out, a terminal strip to provide for what the 425K calls the T and S terminals.

[poplar1]

Northern used "X" and "Y" on their 425QE1 network, rather than "T" and "S."
http://telephonecollectors.info/index.php/document-repository/doc_details/2400-2500-type-desk-and-wall-phones-ne-2500d-tl

[andre_janew]

I had to ask as I'd never seen a 425E on a touch tone phone before.

[Phonesrfun]

My two WE 1500's have 425G networks, which is the same as the 425E network, but less the dial RF suppression capacitor on terminal F.  The attached BSP section (Courtesey of the TCI technical library) shows arrangements for the 425B, E or G networks. 

See the pdf attachment page 3.

There is also a diagram in the wiring diagrams section of the TCI library of a Stromberg Carlson 1500 featuring a SC 425G