The horn is skipping. The skips are just so short you can’t tell.
There are 7002T’s that skip, and don’t skip. The ones that skip are the ones that you and me are fond on (the 7002, 7002T, 7001, V7001, etc.) And there are ones that don’t skip, like the 34T+WS24VDC (4-wire 7002T) is what people call them. And the 7004’s and 7004T’s don’t skip due to the voltage that’s being inputed (I think). And no, another enthusiast told me that Wheelock never made a “flush” mount 7004, but there is a 7003 which is (what i’ve heard) a 4 wire, flush 7002T.
There was also the F34T-24-WS, which was actually the 4-wire version of the 7001T. So far, there is only one source, a video by The Blue CFL who sadly passed away in 2021. The 7003T was an AC-powered horn-strobe like the 7004T, and was 2-wire. Since we haven’t seen one yet, all we can do is speculate (there is a lot of speculation that the 7003T was flush mount but we don’t know yet).
My thinking is that the 7003/7003T series was incredibly rare (like some 30-series horns like the 32P-24), and it was discontinued in the mid-to-late 1980s. The regular 7003 (pigtail connectors) was the first to be discontinued, then the 7003T (screw terminals) sometime after that.
Yes, there are 7002Ts that don’t skip; and the model number is 34T-24-WS. The reason for them not skipping is because they’re four-wire devices in which the horn and strobe are wired separate. In contrast, the strobe on the 7002T gets its charge from the horn’s coil, and thus can’t operate by itself. And so every time the strobe flashes, it draws power from the horn, resulting in the skipping sound the 7002T is known for. The four-wire models were far more ideal for being set to march time or temporal, and were capable of doing audible silence.
As previously mentioned, there was also the F34T-24-WS, which was the flush-mount version and looked identical to the 7001T. Then there was the 34-24-WS, which was the same thing as the 34T-24-WS except it had pigtail wiring instead of screw terminals. Last but not least, an even less common model was the 32PT-24-WS.