401B KTU use

[Rokumoncat]

Hi again,

I just procured myself a Western Electric 401B manual intercom KTU. Has anyone ever used one of these? What do I need to know about using this KTU? The only documentation that I could find is a small two paragraph section in a general 1A2 BSP.

Thank you very much in advance!

Best,

Joe

[poplar1]

These fit in the same slots as 400-type cards, though it may be restricted to the last slot on some systems. They were used for "manual" intercoms, that is, they provide only the talk path (24 Volts DC, filtered, on pins 3 and 18 IIRC) and lamp supervision to show the intercom path in use. Separately mounted keys,  with one or more buttons, were used to signal the desired station. Hence the term "buttons and buzzers" for this arrangement.

[andre_janew]

I'd love to see a picture of it.

[unbeldi]

The 401B replaced the 401A, which is actually the more interesting card for hobbyists, because it has some spare contacts on the A relay for controlling other devices.  The 401B omitted this feature.

The 401B also omitted the choke to decouple speech from the talk power supply, I think, so all that's left on the card is one relay, right?
If you have to save a slot in your KSU the relay could easily be mounting elsewhere.

[Weco355aman]

Here is a photo of a 401 KTU
The BSP number is 518-215-402 page 4 july 1980
I have a spare set of BSP's if you need them.

[poplar1]

401A diagram