Telco collector or restorers spare part
An IDF (intermediate distribution frame) is used to cross connect the telco user cable to individual user line circuits or an IDF can serve as distribution point for multipair cables from a MDF (main distribution frame)
Normally you will see a pair of these (at least), with the lines on one block and the user cabling on the other block and cross connections are made using "jumper wires" usually colour coded red and white (A & B of a 2 wire circuit)
I only have ONE IDF block, so if ever a demonstration system was being setup you would need to source another IDF block to mate with this one (or you may have one already - lucky you!)
Primarily I offering this item for historical purposes although it may still find a use where it is desirable to have an access point (for testing or fault finding) of a multi-core low voltage/signalling cable
IDF's & MDF's still exist but the modern versions are much different from this one - typically thermoplastic construction with "push on" insulation displacement connections using a special tool - Krone is a well known manufacturer of this equipment.
20 Pair IDF Block
Dates from between 1940 and 1950's
All black bakelite construction (block and lid)
Pressed into the block base is a circle and within the circle
I have hunted for any information about who may have made this block but have come up with zilch information
20 pair on one side, 20 pair on the other side (the terminals are through connected, not insulated between each side)
Solder terminals - clean and reuseable (the terminals are shaped and usually the bare wire is wrapped around the terminal a couple of times and then soldered, this gives a very strong and electrically sound connection)
All previous "tails" removed
The block is actually constructed as 5 separate sections, all bolted together so you can access and remove the solder terminals if required.
Metal knurled lid securing nut.
Clean and shiny - I am pretty sure this has had a lacquer applied to the top surface
No cracking BUT I can see a light stress mark where the lid securing screw has previously been tightened too much - it has not cracked but I can see stress in the bakelite
I have checked that this is indeed bakelite and I have no doubt about the material. Rubbing with a cleaning solution leaves a yellow/brown residue on the cloth, also when heated (hot water) it gives off a slight formeldahyde smell and a heated pin does not "melt" into the bakelite material.
Bakelite is actually a really good material for electronics in particular, just a pity it is difficult to "work" and pretty brittle - handle it with care, particularly the lid.
Supplied with the original wooden supporting "backboard" - solid timber. I will not supply the two wood screws required for mounting onto the baseboard though (there are 2x countersunk 6mm holes in the base of the block and you need around 20mm in length for the wood screw)
Weight: (with baseboard) 800g or without baseboard 600g
Dimensions: 190mm x 90mm wide x 95mm high