Defining that method of working has proved somewhat difficult (as a mini-debate in the Forum of
http://www.signalbox.org a few months back demonstrated, with no clearly agreed conclusion).
When King's Cross miniature-lever
(1932) box (KC) was still operational
( : in the '60s, despite Potters Bar NX Panel box's existence, KC was still often referred to by Area staff as 'the power box'), Goods & Mineral box had an acceptance lever (36) to KC for the Down S.London Goods, as did Holloway South Down for the Down Fast and D.Slow (& Copenhagen Junction before that, when
it was the main line fringe box from KC).
However, unlike the DF and DS, the DSLG was not track-circuited, from just clear of KC176 points (DS-DSLG), to G&M's DSLG Home signal (34; as stated previously, on a moderate straight post opposite G&M box).
There was however, what appeared to be rotation locking between 36 and 34 levers (36, once pulled, and put back, could not be pulled again until 34 had been pulled and replaced).
[Before Copenhagen was abolished, and with it, 'the Lickey' (the short, steep connection from G&M down to the Down Slow), G&M's Home signal was a 2-arm left-hand 'gallows'-style bracket standing on the right of this line, with the right hand arm (35) being for DSLG to Copenhagen Jn. and the DS.]
Although I got to know the box pretty well, I now forget about the Box Special Instructions, but I
think that, for through trains from the DSLG to the Down Goods and on to Holloway, G&M had to have 'got the road' forward and pulled off Home and Starter (there was no Distant;
KC164 and 194 only cleared to yellow for this route) before accepting the train from KC; not only to avoid trains possibly being long enough to stand back foul through KC's points if held at G&M 34, but also to reduce the likelihood of trains being checked/stopped at G&M's signals, and then being unable to get going again because the DSLG, though short, was so steep. I think light engines were probably exempted from that though.
Regarding KX PSB, built behind York Road platform, although erected by 1971, and taking over from the 1932 box ; until March-April 1977 when the Kings Cross station area was remodelled and resignalled, (with a few minor exceptions) the new box merely took over the existing KC signalling (keeping that prefix and all its numbers), but worked temporarily (nearly 6 years) from a large individual function switch panel.
This was still the situation when Goods & Mineral, KX Goods Yard, and the Down South London Goods, were reduced, or simplified and/or closed, for the remodelling works to start for the future new Slow lines to run through the western bores of Gasworks and Copenhagen Tunnels, including realigning and re-levelling the Up Goods-DSLG formation and alignment between the tunnels, for the new Up Slow/No.2 Slow, and demolishing the eastern edge of the goods yard for the No.1 Slow/Down Slow to run parallel next to the US/No.2S.
So the King's Cross PSB's 'proper' panel (the NX ; prefix 'K') never worked with Goods & Mineral on any line, as it had been abolished by the time that K was running the new Slow lines, and the simplified Goods Yard access (with connection to the North London Incline) was a connection (K2037s) off the new Down Slow just south of Cop'n.Tunnel : The yard's north end connections (still recognisible as remnants of G&M's layout) became worked from a tiny single-storey brick built 'box' named Freight Terminal Junction (FT), which also worked the NL Incline connection [with Camden Road (CR), still rather like a signalled through siding] and a release to K for 2037 points.
As you probably know Micky, the NLI was subsequently upgraded to bi-di running line signalling standard (about 1988 I think) and transferred from FT to K control, still fringing with CR. And later still the goods yard closed completely, so all that's left of all that now is the NL Incline (its lower portion realigned and significantly re-levelled when the 'HS1' CTRL was constructed alongside) still connecting with the Down Slow at the south end of Copenhagen Tunnel, at a location now renamed back from Freight Terminal Jn. to Copenhagen Jn.