On 9/5/2012 8:03 PM, Dan Marotta wrote:
The TT22 doesn't cost that much more than the TT21.

I didn't think that the cost difference was the deciding factor here....
power consumption was. However, looking at the specs, there's not a
whole lot of difference.

TT21 - Idle: 0.15 A; Active 0.28 A
TT22 - idle: 0.15 A, active: 0.34 A.

Both sets of numbers are at 14VDC - so, 3.9 vs 4.8 Watts when
interrogated - which is (hopefully) a fraction of the total time.

Tony "6N"

Source:
http://www.sea-avionics.com/lc/cart....bstrin g=tt21
http://www.sea-avionics.com/lc/cart....bstrin g=tt22