Quote Originally Posted by angelozip View Post
I found very interesting this possibility, but noted that the problem of the limit of installed subscriptions happens with different GPS devices with the same GTM25 cable, which apparently indicates that signatures are in gtm25 receiver, unless there is some logical problem with my cable.

Giomen when you researched the 41 region, you could tell which GTM cable you used? I ask because I have read in this forum that older models of cables, such as the GTM 10, 12.. and older, do not stored the subscription on the cable, so just might be in some region of the gps memory. .........
I'm not quite following all this at the moment in regard to storing of codes.

As Angelo says, GTM2x > receiver stores the subscriptions, and also it has the codes on it exclusively surely? Old receivers GTM1x handle things differently and i know Loly understands the functional differences between 1x and 2x/3x much more fully then most ppl [certainly more than me, anyway], but the subscription is still stored on the receiver of GTM12. If the sub and code were only stored on the unit, in rgn41 or elsewhere, of that unit originally used to enter the code to unlock the sub then a GTM12 couldn't be be used on other compatible units so must be on the receiver. Maybe the code also gets written into another unit's rgn41 from the receiver to make it usable? If that's so, a clean NV would simply have the codes rewritten to it anyway. BTW, i haven't been able to write 3xx/6xx rgn41 to SD like it's other regions [5, 14, 15 etc], but 41 can be erased. So the point of using a clean 41 with older units to reset anything may be totally moot regardless [and with new units too]:

I doubt Garmin writes new devices firmware from scratch if that can be avoided. Rather they would modify/expand/amend existing to suit if they can. Assuming Giomen is talking about fw of a device later than 3xx, could the reference to GTM codes discovered by him in that fw simply be an unused legacy placeholder from earlier device software used to enable subs from unit to unit by copying from the GTM1x receiver to the different unit? Certainly on my GTM12 the sub will show as only 'New Subscription' until a sat fix and fm reception. Maybe GTM12 works differently to GTM10/11 as the GTM12 FM receiver module is quite different to them and seems the same as GTM21. GTM20, 25 & 35 all seem to be similar module and only differ in the charging plug/device connection.