Re: [PSUBS-MAILIST] RFC - Standard Thru-Hull Electrical Connector

[Jon Wallace <jonw@psubs.org>]

Sean,

I like the way you think out of the box, and you've raised some 
excellent points, thanks.  Regardless of whether the unit is used as 
general purpose, 2-wire w/auxiliary, or 4 wire dedicated comms connector 
I think you are correct that we should include a pin-out as part of the 
standard.  We can attach a small drawing to the standard that 
illustrates the pin-out.  It sounds like the current proposal is not 
specific enough and we need to choose whether the connector is a 
dedicated 4-way comms device (and the home built units will have to 
adapt to it if they can) or if we want the connector to be a general 4 
pin connector which could have many uses, one of which is the use that 
Alec originally intended.

Four pins equals a lot of options and so determining the pin-out is 
important

one hot, one data, two common
one hot, two data, one common
two hot, two common
three hot, one common
many more possibilities....


Jon



Sean T. Stevenson wrote:
> With regard to the proposal, if this is indeed intended to be a 
> standard connection for communications devices, I suggest that it is 
> not sufficient to describe a physical connection without also 
> describing a proposed standard pin assignment and operating voltage.  
> Your proposal makes specific reference to diver units made by OTS and 
> Divelink, indicating that these units operate in a two-wire mode.  
> Two-wire (push to talk, or PTT) units are common in low-cost devices, 
> but most commercial diver communications setups are four-wire 
> (round-robin, or open-circuit), both for reasons of improved safety, 
> hands-free operation, and natural communication flow without 
> necessitating radio protocol interjections in the conversation.  The 
> proposed application combining comms and hydrophone is functionally 
> identical to implementing communications in the four-wire mode - 
> namely, a transmit circuit (hardwire umbilical to diver earphones, 
> ultrasonic transducer for diver or sub-to-sub wireless, submersible 
> speaker, etc.), and a receive circuit (hardwire umbilical from diver 
> microphone, ultrasonic receiver for diver or sub mounted transmitter, 
> hydrophone, etc.)
>
> As such, any proposed standard should accommodate both two-wire and 
> four-wire communications implementations, but should standardize the 
> pin assignments explicitly for that purpose.  Additionally, where you 
> propose that the standard connector be implemented for communications 
> in two-wire mode, thus making available the other two pins for 
> auxiliary devices, my immediate reaction is that this practice should 
> be avoided, if for no other reason than it then becomes a standard 
> which isn't.  More pragmatically, you must ensure that any voltage or 
> current present at these auxiliary pins remains compatible with any 
> possible four-wire system which may be connected to it (in keeping 
> with the spirit of the standard design), even if the operative 
> equipment within the sub is PTT.
>
> This raises the question of whether we should standardize on four-wire 
> open communications systems (or four-wire implementation, even if the 
> operating equipment is PTT), since this avoids entirely the 
> possibility of lost communication due to transmit/receive timing - not 
> a huge issue with a single communicating party familiar with radio 
> procedure, but arguably necessary in the presence of multiple parties 
> communicating on the same frequency.  In the case of through-water 
> comms (ultrasonic), this theoretically opens the door to a natural 
> conversational environment between several submerged subs, which I 
> hazard a guess would appeal to many in the community.




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