User manual Descent Mk2 pressure sensor

7000518 said:

i prefer not to mount the transmitter directly onto 1st stage but use a short hose,

If you can mount it directly on the 1st stage, you can mount it on any pressure hose of your preferred length, too. There is no reason though that it has to be the same lenght as the SPG hose, as you seem to be afraid of. For having the emitter more than 7cm from the body, you do not need any long hose. As written in the manual, it is sufficient to mount it directly on the first stage (as long as it does not point directly to your head). The minimal distance is pretty standard for any emitter (regardles whether radio or sonic).

I agree, but while youd expect any signal to be omnidirectional, i wonder if the sonographic part, rather than high frequency on land transmitter, is directed to transmit forward and side only hence the line of sight clearance of your head as you mention, not sure, clearly theyve done this because of signal dropout, though given the multiple links stated maybe its aimed at diveschools taking groups down, interesting to see how this plays out in practice and reasoning behind this, it would be interesting to see a tear down of the accoustic transmitter 

Does the sonar part of this device mean, that only this transmitter will match with the mk2i?

It looks that way, it appears to switch between the two types of transmission depending on whether youre in water or not, theres not enough info but seems you couldnt link it to other computers that dont have a sonar reciever