Older British symbol on a flow diagram - Page 1
Forum section: electronics / beginners

author: Alikev42
author_rank: Newbie
timestamp: June 10, 2020, 07:02:30 pm
content: Hi, there,I'm a repair technician for an analog audio company trying to decode the flow diagram on the back of a product first made in the mid-to-late 1990s. I know I'll smack my head when someone else out there says what it is.https://www.eevblog.com/forum/Smileys/default/bangheadonwall.gifThe symbol leads from an XLR mic input connector to a switch as can be seen in the attachments. As mic level is about -30 dBu and pro line level is about +4dBu, I thought the symbol is an odd sort of amplifier, but there are other triangular amps in the diagram. Is it possibly a isolation coupler of some sort? I've not seen that in other circuits I work on.I have reason to suspect this is British since the product was produced in Britain (wow, what powers of deduction!) Some of the symbols in schematics from these older products also from Britain are different from those I learned getting my EE in the early 1990s. By context (consymbol?) I can figure out most of them. Image searches are not proving as helpful as I would like them to be.

author: Monkeh
author_rank: Super Contributor
timestamp: June 10, 2020, 07:04:53 pm
content: It's a transformer.https://www.iso.org/obp/ui#iec:grs:60417:5156

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 10, 2020, 07:09:55 pm
content: I had seen this symbol in old Italian-made industrial products.The symbol kind of gives you a clue; the two separate but interleaving circles make you think that the signals are separate yet somehow coupled together.

author: Cerebus
author_rank: Super Contributor
timestamp: June 10, 2020, 07:11:02 pm
content: Yes, and it's an IEC symbol - nothing British about it in particular.

author: TimFox
author_rank: Super Contributor
timestamp: June 10, 2020, 08:51:59 pm
content: On that diagram, it must be a transformer. However, that symbol with two overlapping circles is often used to denote a current generator.

author: Alikev42
author_rank: Newbie
timestamp: June 10, 2020, 09:18:06 pm
content: Hi, everyone,Thanks for the info. I am more used to seeing a different transformer symbol, those on the right in the attachment. I did do a search for electrical transformer symbols, and found that picture. If that photo is to be believed (and if it's on the internet...), then the overlapping circles is an architectural version of the same or similar device. I don't speak architecture (very well), so I'm not surprised I didn't recognize the symbol.The schematic I have for the device is hand-drawn and uses the more familiar symbol. Please forgive my ignorance.

author: Alikev42
author_rank: Newbie
timestamp: June 10, 2020, 09:23:51 pm
content: Hi, TimFox,I honestly haven't seen the overlapping circles used for a current source. My schooling always used the arrow in the circle or rhombus. Unless you're differentiating between current source and current generator?

author: cdev
author_rank: Super Contributor
timestamp: June 10, 2020, 10:00:03 pm
content: It's thefist-bumpsymbol of course..

author: TimFox
author_rank: Super Contributor
timestamp: June 10, 2020, 10:02:42 pm
content: There are many symbols for a current source. This link shows five. I first saw the linked circles in elementary transistor texts, ca. 1966.https://commons.wikimedia.org/wiki/File:Ideal_current_source_symbols.svg