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.2) Manual party lines were sometimes identified by a letter suffix. Therefore, there was a sixth column of four letters on the display screen.
The literature suggests Panel had extra registers for these suffix and prefix digits.
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.
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? And for panel areas, was a number listed as "PEnnsylvania 6-5000 J"? Did someone dial that extra letter?
d) Theorectically, it would be possible to have two extra digits: "PEnnsylvania 6-10300 J", meaning someone would dial nine numbers. But did this actually happen in practice?
I really question the 10,500 line exchanges. But undoubtedly some parts of New York City had plenty of manual party lines when Panel was first deployed, and thus require the letter suffix.
Another question:
e) The literature says that if a customer dialed a number that was a toll call, the Panel system routed it to an Intercept operator to make out a toll ticket. Was the operator able to take advantage of the fact the customer already dialed the number, or did the customer have to give it to the operator and she redialed it?
This was a little tricky to explain, but I hope it's understandable. Thanks for your help!
[public replies, please]P.S. The logic employed by the Panel Switch and the hardware to implement was very impressive, considering it was in the 1920s!