-----Original Message-----
From: Tony Renshaw [SMTP:renshaw@ozemail.com.au]
Sent: Saturday, April 19, 1997 2:21 PM
Subject: Re: trim buttons
>Two SPDT push buttons (Fig. 4 of the MAC info.) gets away from the doubtful
>rocker switch. Furthermore if each is actually a DPDT, wiring the halves in
>parallel give the redundacy needed to overcome dirty contacts. Doesn't guard
>against sticking down so you still need an isolate, but only one thing to
>press at a time. Pressing both by accident is safe .
The jargon got the better of me here, and as I would like to understand what
you are talking about Graham, can you please explain:
2)What a SPDT and a DPDT is?
Some Switch Terms
SP - Single Pole. - the switch is capable of making and breaking one circuit
DP - Double Pole - the switch is capable of making and breaking two circuits
ST - Single throw - the switch has two positions - on and off
DT - Double throw - the switch has three positions - usually on - off - on
NC - Normally Closed ie ON
NO - Normally Open ie OFF
Momentary - the connection is made against spring pressure and then releases
Double pole switches are sometimes wired with both poles connected together to
create a single pole switch. This way you get a backup connection within the
switch
So if someone presents you with a switch labelled as
you now know that it can handle two independent circuits and direct the output
of those two circuits to two wires, either of which can be on at any one time.
I am sure Bob will let you know how to get hold of a copy.
(Bob - the address for my commission cheque is....... :))
Tony
Tony Krzyzewski Kaon Technologies Ltd
Managing Director PO Box 9830
Ph 64 9 358 9124 Auckland
Fx 64 9 358 9127 New Zealand
tonyk@kaon.co.nz
Networkers visit: www.kaon.co.nz
Aviators visit: www.kaon.co.nz/europa/272index.html
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