One of the design points of Panel Switching was that > calls to/from manual customers would appear identical to > the customers. That is, dial customers did not have to > know if they were calling a manual exchange, they'd still > dial the number, and manual customers would simply pass > the number to their operator.
> To accomplish this, manual exchange switchboards > connected to Panel systems were equiopped with a light > display screen. This would light up digits for the > desired number (from a dial customer) of the desired > manual board subscriber. (The Panel exchange would send > appropriate coded data to light the screen). The operator > would read this and plug into the right jack.
> All the texts note two interesting twists to this:
> 1) Manual exchanges could have 10,500 lines, not merely > 10,000. Therefore, there was a fifth digit on the display > screen...
> My questions, if someone could help:
> a) Has anyone ever heard of a manual exchange that had > more than the 10,000 lines? I suppose these were in New > York City where Panel was originally deployed. My guess > is that outside a large city they'd be extremely rare.
> b) If calling such an exchange and a number above 10,000, > did a dial user dial an extra digit? Was someone's > number listed as "PEnnsylvania 6-10240"? That would mean > dialing 8 digits.
There was a thread about this on the TCI list a few years ago. Steph Kerman, one of the regular TCI contributors, explained it as follows:
AFAIK, even manual offices did not have numbers greater > than 10,500, which I have seen stated in many places over > decades as the maximum number of jacks that could be > placed in front of an operator. With the conversion to > dial these last 500 numbers posed a problem since they > exceeded what could be represented with a 4-digit number. > Dial customers had to dial 8 digits to reach these > customers. The equipment was designed to wait for a > possible 8th digit if the first numeral was a "1". The > building across the street from me is shown as having had > RIVerside 10125. I see many other 1xxxx listings.
So yes, a number such as "PENnsylvania 10240" was indeed dailable, the cue to the equipment being the "1" as the fourth digit. But it would have been listed as 3L+5D, not 2L+6D as you suggest.
c) I know in some directories party line subscribers were > listed with their letter suffix: "Main 1234 J". But did > people _dial_ that letter as a suffix?
Apparently seven-digit numbers in the form "Main 1234 J" did exist somewhere. Miller (McGraw Hill 1933) cites the following directory listings in Figure 8, page 20:
Miller doesn't tell us where those numbers were located, but streets named Frontenec, Champ de Mars, and Parthenais exist in Montreal.
And for panel areas, was a number listed as "PEnnsylvania > 6-5000 J"? Did someone dial that extra letter?
The only 8-digit dialable numbers (within NANP) I've ever heard of were the 3L+1+4D numbers in NYC.