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barnacle
PostPosted: Wed Mar 01, 2023 5:05 pm 
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Location: Potsdam, DE
As I said: I studied electronics with the BBC long enough ago that we studied the gm curves for valves and basic valve circuit topologies; there was still a lot of equipment using valves. Two years later when I finished the qualification, the section on microprocessors was _after_ the final exams. It wasn't well attended :mrgreen:

Neil
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kernelthread
PostPosted: Wed Mar 01, 2023 9:56 pm 
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Joined: Wed Jun 23, 2021 8:02 am
Posts: 165
The first circuit diagrams I ever saw (late 70s) used TR and IC designations. They also used a naming convention for relays where the relay coils were labelled RLA, RLB, RLC etc. and the sets of contacts were labelled with an additional number, so the first set of contacts on the first relay would be RLA1 and the second set of contacts on the third relay would be labelled RLC2 etc.
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BigDumbDinosaur
PostPosted: Thu Mar 02, 2023 12:25 am 
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kernelthread wrote:
The first circuit diagrams I ever saw (late 70s)...used a naming convention for relays where the relay coils were labelled RLA, RLB, RLC etc. and the sets of contacts were labelled with an additional number, so the first set of contacts on the first relay would be RLA1 and the second set of contacts on the third relay would be labelled RLC2 etc.

That naming scheme is something that became fairly common in railroad automatic block signal system (ABS) schematics early in the 20th century, as well as in electromechanical telephone exchange circuits (which have a huge number of relays). Autophone step-by-step telephone PBXs (Autophone is/was a UK company) used a fractional notation for relays in their schematics, such as illustrated in the following:

Attachment:
File comment: Fuel Pump Control Module
fuel_pump_ctl_schem.gif
fuel_pump_ctl_schem.gif [ 24.82 KiB | Viewed 327 times ]

In the above, a rectangle with “fraction” next to it represents a relay’s coil, the number within the rectangle being the coil’s approximate cold DC resistance in ohms. The fraction’s “numerator” is the relay name and the “denominator” is the number of active contacts in the circuit, which may be fewer than the number of contacts in the relay. For example, EOP/1 is the Engine Oil Pressure relay, has one active contact and a cold coil resistance of 960 ohms.

Contacts are designated with the fraction’s numerator, i.e., relay name, to which is appended a number from 1 to N, N being the number of active contacts in the circuit, for example, EOP1, the only active contact for the Engine Oil Pressure relay. This arrangement works well with detached contact notation, and makes for a less-cluttered and easier-to-read schematic, especially when the relay count may number in the hundreds or thousands.

In step-by-step systems, a separate notation was used for rotary stepping relays. That notation varied, but typically indicated the relay name, coil resistance, number of discrete positions in use and the number of banks of contacts. Double-motion Strowger relays used a sort of X-Y notation, since the relay would first step vertically to a bank of contacts and then step horizontally” (in rotation) to align to a particular contact on the selected bank.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!


Last edited by BigDumbDinosaur on Thu Dec 28, 2023 11:27 pm, edited 1 time in total.

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BigEd
PostPosted: Thu Mar 02, 2023 8:02 am 
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PC Building Yoshi wrote:
Also, Thank you for all of the information and help with this reply! especially the USB-to-Serial Info!

Hope you're still enthused and still on track Yoshi. As this thread has drifted, I recommend you start a new one if you have an update or further questions.
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