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