I didn't have my glasses when I read the original post and couldn't see that the needed relay has to be AC. Sorry. Depending on the number of contacts in the relay, you can use a contact to hold the relay energized until the power source is removed from the contact.
yes, I've tried several electronics websites, but 10 to 12V AC latching relays are pretty rare.
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Look through Digi-Key for latching relays. But I doubt that you will find one cheaper than the one you mentioned above.
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I use relays I buy from allelectronics.com. They are DPDT 12 volt relays, part #RLY-622. My signals are activated with NCE BD20 current detectors. The track relay needs to be stuck up (latched) by one of its own contacts when the current detector shuts off. The DC power to keep the relay stuck up comes from the next signal location. I do use two relays per detector to get enough contacts to work the stick feature plus operate the home relay. The relays are $1.75 but ten or more are only $1.50 each. I built several T-Trak modules with working 3 color signals that work good. I mount the relays on PC boards from Radio Shack that will hold four relays.
I'm setting up an analog Marklin Z-scale layout and using latching relays for block signals with automatic running. Marklin sells a 10V universal relay (8945), but I was wondering if there are other (cheaper) alternatives? Transformer voltage is 12V AC. I've tried a Viessmann relay (5551), but it needs 14V and doesn't reliably switch at 12V. Atlas snap relay specs say they also needs a higher voltage. Electronic protection if the control pulse gets stuck on would be nice, too, to prevent burning up solenoids. Any ideas?