[Elecraft] The state of a latching relay

[Tom Hammond]

Sverre:

>If I understand right, the latching relays in the K1 and K2 change state
>every time you give them current for a short while, and then stay in the
>new position until the next impulse is given to them. To my mind this
>makes it impossible to figure out which position they are in, but I'm
>probably missing something here.
>
>So the question to the clever ones is: How does the firmware in the K's
>know the relay settings?

1) It remembers what band you're on and which relays should be reset for 
that band. It may 'cycle' all relays upon turn-on as well, and then reset 
them to the last band.

2) The relays only change state if they are given the correct POLARITY 
signal as well... one polarity SETs and the other RESETs.

3) Since the relays DO latch, if you select a band and then turn the radio 
off, the relay will remain in the appropriate state for that band. So you 
can then use an ohmmeter to perform a continuity test on the relay contacts 
to verify that it really is SET (or RESET).

73,

Tom  N0SS