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Old 8th Mar 2021, 3:40 pm   #1
Telephone Guy
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Default Free-standing telephone keypad

Hi,
Can anyone tell me if it's possible to buy a free-standing telephone keypad with just the basic 1 - 9 and # and * keys that I could plug in alongside an old 746 or similar ( so, activate the keypad, dial the number, pick up the receiver on the 746, deactivate the keypad ... or something along those lines )? I have a couple of old 746s that work fine, but dialling anything up to eleven digits longhand is a pain!!
Thanks.
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Old 8th Mar 2021, 4:34 pm   #2
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Default Re: Free-standing telephone keypad

You used to be able to get a little unit slightly smaller than a fag packet with an LCD display, a keypad and a speaker in it. It had the capacity to store telephone numbers as well as allowing direct dialling.

It was acoustically coupled with the speaker on the telephone handset mic and then activated. I have a Tandy one somewhere.
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Old 8th Mar 2021, 4:44 pm   #3
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Default Re: Free-standing telephone keypad

Quote:
Originally Posted by russell_w_b View Post
You used to be able to get a little unit slightly smaller than a fag packet with an LCD display, a keypad and a speaker in it. It had the capacity to store telephone numbers as well as allowing direct dialling.

It was acoustically coupled with the speaker on the telephone handset mic and then activated. I have a Tandy one somewhere.
Sutch keypads, usually without LCD or memories were often supplied with answering machines so you could input a PIN to retrieve your messages before DTMF phones were the norm.
Most mobile phones produce DTMF confidence tones as you dial through the speaker, so you could use that instead.
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Old 8th Mar 2021, 6:15 pm   #4
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Default Re: Free-standing telephone keypad

there's a battery operated tone dialler here: (no connection, no pun)

https://www.ebay.co.uk/itm/274688503...12041000008005

These were, apparently used to dial-out on privately owned payphones connected to a standard phone line to circumvent the coin slot.

PS the link also shows 'suggestions' for many other types in a similar vein.
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Old 8th Mar 2021, 6:22 pm   #5
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Default Re: Free-standing telephone keypad

At work I have a couple of tubes of an obsolete IC which I believe is a keypad-to-DTMF-tone encoder IC, it was probably the basis of at least some of the self contained DTMF keypads like the one McMurdo pointed to.

I'll dig them out to see what they are - probably just needs a keypad, a crystal and a sounder / speaker of some sort.
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Old 8th Mar 2021, 7:33 pm   #6
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Default Re: Free-standing telephone keypad

There were devices designed to facilitate telephone banking in the olden days too. https://www.ebay.co.uk/itm/233923479...84.m1555.l2649
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Old 8th Mar 2021, 10:48 pm   #7
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Default Re: Free-standing telephone keypad

Indeed there were! I banked with NatWest once upon a time and they issued me with one identical to one linked to by pip5678. I still have it here somewhere and it was still in working order last time I pressed its buttons, but its battery may be flat by now. One thing I found, however, is that they don't work well with the 200- and 300-series telephones' carbon-granule transmitters.

I think, however, that Guy is looking for something stand-alone to plug in rather than an acoustic DTMF keypad. It would effectively be a telephone with a switch instead of a handset and cradle.
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Last edited by Dave Moll; 8th Mar 2021 at 10:56 pm. Reason: rephrasing of final paragraph.
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Old 9th Mar 2021, 12:32 am   #8
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Default Re: Free-standing telephone keypad

If you have space, use a two way socket adaptor and a cheap second modern phone to do the dialling. When connected, lift handset of old phone and replace handset of modern phone.
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Old 9th Mar 2021, 7:28 am   #9
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Default Re: Free-standing telephone keypad

Hi, and thanks for all the replies. There isn't really enough space to put a modern phone alongside the old one in either of the locations where the 746s would be going, unfortunately ... that would certainly solve the problem.

I've checked out the other links and am considering those as alternatives ... don't mistake this for ingratitude, but ideally, what I was looking for was something that would actually plug into the socket alongside the 746 ( i.e. using a double adapter ) or even something that would go in series with the 746 ( so, the 746 plugs into the free-standing keypad which in turn plugs into the wall socket ). With the ones I've seen in the links provided, you have to hold the speaker of the free-standing unit up to the mouthpiece of the phone whilst dialling the number ... I can see how that would have been regarded as cutting-edge back in the day, but maybe more cumbersome than it's worth now!

I did use to have one of these; it was designed for use with a headset but worked perfectly well as described above. Unfortunately it eventually gave up the ghost and doesn't appear to be manufactured any more. The nearest equivalents I can find either only come with headsets and / or are prohibitively expensive.
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Old 9th Mar 2021, 10:40 am   #10
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Default Re: Free-standing telephone keypad

If you want to try to grow your own solution, the ICs I have are TP5089N. They look quite handy for this sort of purpose.

They require very little other than a 0-9 + *, # keypad (widely available) + a common 3.57Mhz crystal. They run from a very wide supply voltage range. It would be up to you to make the interface between the IC output and the line.

If you think they might be any use, PM me and I'll bung you a couple along with matching 3.57Mhz crystals.

http://www.repeater-builder.com/tech...mf/tp5089n.pdf
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Old 9th Mar 2021, 2:14 pm   #11
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Default Re: Free-standing telephone keypad

Hello Sirius,

Thank you for the very kind thought, but although I have some electronic know-how, I don't think I have either the skill or the wherewithal to pull that off.

One thought that did occur to me - although I'm extremely dubious, for the same reason - is that theoretically, it presumably wouldn't be that difficult to connect the speaker wires from any of the units in the links provided so far to the speech wires of a phone plug ( RJ11? ) - always assuming I could get hold of an RJ11 plug that was already wired to an ideally quite short length of cable with some sort of terminals on the other end, it being the case that many of my previous attempts to work with the kind of 'tinsel wire' normally found in phone leads has not ended well!

Ideally though, I'd really rather not have to do any kind of surgery at all ... I'm getting the impression that units that fit the description of what I'm looking for simply don't exist any more ( except, as I say, ones that either come with headsets and / or are ludicrously expensive ). Is that the case?
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Old 9th Mar 2021, 2:24 pm   #12
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Default Re: Free-standing telephone keypad

Just an afterthought, although like the previous one, I suspect there will be reasons why this isn't feasible ... still:

As an alternative to the free-standing keypad idea, is there any ( relatively simple and painless!! ) way I could use the numeric keypad on a computer to do the same job, if the computer were to be plugged directly into the phone line? Is there some sort of ( legal ) software that I'd need, that would do this? - is it even safe to plug a computer directly into a phone line, and what output on the computer would I need to use? ( The most obvious answer would seem to be the audio output, in which case, would I be able to get what I assume would have to be a 3mm jack plug to RJ11 phone plug cable? )

So many questions, so little time ...!
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Old 9th Mar 2021, 4:08 pm   #13
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Default Re: Free-standing telephone keypad

In theory you could use an old computer with a Hayes-type dial-up modem installed to generate DTMF tones but the terms 'sledgehammer' and 'nut' spring to mind.

To answer your other question you can't really directly connect a tone generator to the line because of the DC voltage which will normally be found there, -50VDC when the line is off-hook. If you look at the application circuit in the datasheet for the chip I linked to in #10 you'll see that they use a line barrier transformer to isolate the circuit from the line. Anything you do will have to do something similar to separate the unit from the line.
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Old 9th Mar 2021, 4:17 pm   #14
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Default Re: Free-standing telephone keypad

How about a real cheap DTMF 'phone, this one from Argos may well work without the handset plugged in.
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Old 9th Mar 2021, 4:31 pm   #15
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Default Re: Free-standing telephone keypad

If you unplug the handset from a 'phone, won't you disconnect the loop? I assume you would need some sort of connection across the transmitter terminals in the 'phone to restore continuity of the loop.

By the way, the above post appears to be intending to contain a link.
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Old 9th Mar 2021, 4:59 pm   #16
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Default Re: Free-standing telephone keypad

Quote:
If you unplug the handset from a 'phone, won't you disconnect the loop?
Maybe not with all the electronics in the base already.

Oops, the link... https://www.argos.co.uk/product/3924358
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Old 9th Mar 2021, 5:02 pm   #17
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Default Re: Free-standing telephone keypad

You could try to find a 782R (or 8782R, which plugs straight in).
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Old 9th Mar 2021, 5:52 pm   #18
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Default Re: Free-standing telephone keypad

Call centre base units can be found for about 30 on Amazon. (Example)

Alternatively "mouse phones" were slightly popular and there are a few on ebay
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Old 9th Mar 2021, 7:30 pm   #19
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Default Re: Free-standing telephone keypad

If you can find one of these or something similar on ebay, it should do what you want. Press the round button to seize the line and again to hang up ( when the other end is ringing). However, you will need to plug in a small speaker or earphone to the headset socket.
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Old 9th Mar 2021, 7:31 pm   #20
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Default Re: Free-standing telephone keypad

Forgot to add the picture. One of these...

Much the same sort of thing as OscarFoxtrot suggested.
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