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Old 25th Jul 2020, 5:28 pm   #1
Dave Moll
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Default Why strap T5 to T6 in 700 series telephones?

As per the title, I have never quite understood the purpose of the strap between T5 and T6 in 700 series telephones. Without it, the gravity switch would disconnect the ringer when the handset is lifted, whereas this strap means that it remains connected across the line. Does this have an effect on the speech performance of the telephone during use, or is it simply a hangover from earlier telephones that didn't have a switch contact in this position?
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Old 27th Jul 2020, 6:45 pm   #2
dagskarlsen
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Default Re: Why strap T5 to T6 in 700 series telephones?

Seen from non UK (=Norway) I see no reason for that strap, but we have capacitors in each phone. (no master socket)

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Old 27th Jul 2020, 6:55 pm   #3
Dave Moll
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Default Re: Why strap T5 to T6 in 700 series telephones?

I don't think it's related to where the capacitor is located. After all, the 700 series of telephones pre-dates the introduction of master sockets with capacitors in them - and ringers were connected in series to avoid bell-tinkle when dialling.

The thing that seems strange to me is that a changeover switch was introduced with the 700s (in contrast with the simple switch in earlier 'phones to make a loop) but the chageover contact was shorted out.
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Old 27th Jul 2020, 7:15 pm   #4
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Default Re: Why strap T5 to T6 in 700 series telephones?

The option may have been intended (whether used or not) for some plan systems where the ringer had to be rung (eg to signal an exchange call) even when the phone was in use (eg on an internal call).
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Old 27th Jul 2020, 7:35 pm   #5
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Default Re: Why strap T5 to T6 in 700 series telephones?

Isn't the link removed for shared service working?
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Old 27th Jul 2020, 8:18 pm   #6
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Default Re: Why strap T5 to T6 in 700 series telephones?

I notice that on the cheaper ASTIC-less 'Etelphone' made by Ericsson (N1900) the paster diagram shows the link between T5 and T6 is removed. Drawing N112419/4 refers.
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Old 27th Jul 2020, 8:45 pm   #7
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Default Re: Why strap T5 to T6 in 700 series telephones?

Quote:
Originally Posted by russell_w_b View Post
Isn't the link removed for shared service working?
Yes.
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