(Really) old skool stuff: QCII
Quik-Call II; QCII or Two-Tone was a signalling format developed by Motorola and I think GE in the 1950s for use in pagers. This was before the days of POCSAG and GSM and so in those days you'd probably have something like the Pageboy (below).
Back then, if somebody paged you, the pager would give an alert tone followed by a voice message, usually read out by the dispatcher or whoever was looking for you (depending on the hardware used).
Each pager would have a three (or four) digit code. So if a member of the public wanted to page somebody (e.g. a Doctor) , they would call the paging company or the control room, give the code and the message. The call taker would enter the code on a console wait for the alert to finish and read out the message.
The console would transmit two sequential non-harmonically related audio tones using FM, followed by microphone audio. The tones sent would be based on the code entered on the console.
The above pagers would have two (sometimes three) so-called Tone Reeds installed in them. Each reed (literally a plug in module) would have a three-digit cap-code each and resonant frequency. The frequencies were chosen such that a harmonic would never equal another frequency/cap-code.
The above pagers would have two (sometimes three) so-called Tone Reeds installed in them. Each reed (literally a plug in module) would have a three-digit cap-code each and resonant frequency. The frequencies were chosen such that a harmonic would never equal another frequency/cap-code.
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| Source: eBay Seller |
Inside the reed there was essentially a transducer, attached to a tuned element (really just a ground piece of spring steel). When the received audio contained a specific tone for longer than a few milliseconds, the tuned element would vibrate at its resonant frequency and this vibration would close a circuit.
One reed would go into position A and the other in position B. The paging console would generally send two tones - A and B. If the frequencies of these tones matched those of the reeds, the pager would sound an alert and open its squelch for a defined amount of time. So essentially, the pager was an analogue FM receiver that would only unmute when the correct tones were received (in the right order).
When compared to Select-5 signalling, the duration of each tone in QCII is very long (>1s). This was intentional as most older pagers didn’t have any microprocessors and could not handle things like tone falling and error correction. Later models like the Spirit and Minitor used a processor but the signaling format itself has reminded unchanged.
The pager code is selected/defined by means of a table. So the tones have to be specific frequencies and these cannot be swapped. The frequency selection is quite complex and there are many variations frequency pairs.
When compared to Select-5 signalling, the duration of each tone in QCII is very long (>1s). This was intentional as most older pagers didn’t have any microprocessors and could not handle things like tone falling and error correction. Later models like the Spirit and Minitor used a processor but the signaling format itself has reminded unchanged.
The pager code is selected/defined by means of a table. So the tones have to be specific frequencies and these cannot be swapped. The frequency selection is quite complex and there are many variations frequency pairs.
The first digit of the pager number would determine which two columns each tone (A and B) would come from. So for example, if a paging system used Cap Code Q and the first digit of the Pager's number/code was 2, then the tones for the 2nd and 3rd digit of the pager code would both come from column 2. Then, if the 2nd and 3rd digit of the pager code was 2 and 3 (so pager code 223) then tone A would be 634,5Hz and tone B would be 389Hz.
If you listened in to the above page transmission using a scanner or two-way radio, it would sound like this.
The folk at Midian Electronics have produced a table which you can download. You'll also be able to find scanned copies of old Motorola manuals all over the internet which have a similar table to the above.
QCII is currently only(?) used in the USA. All QCII implementations outside North America have long since been retired. In Germany, some volunteer rescue workers use analogue pagers but these use ZVEI which dates from the seventies.
In non-North America models (i.e. not a XPR____), for QCII to work, you would need to add an Analog Personality. Non-North America models also have the possibility of adding a 5-Tone Personality which does not allow the selection of the below parameters.
If you listened in to the above page transmission using a scanner or two-way radio, it would sound like this.
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| Source: Midians.com |
QCII is currently only(?) used in the USA. All QCII implementations outside North America have long since been retired. In Germany, some volunteer rescue workers use analogue pagers but these use ZVEI which dates from the seventies.
Most MOTOTRBO radios support QCII decode. Higher tier models will also allow the user to page other radios or pagers from the contact list. It's not possible to enter a pager code from the keypad as the pager code is not directly related to the tone pair used (as is the case with Select-5).
To configure QCII in the MOTOTRBO radio, you would use a combination of the following settings:
In Signaling Systems, you would either enable Call Alert Enable or Sel Call Enable. This would give the user the ability to make these two types of calls. I've never tried Sel Call but Call Alert would make the target radio beep only whereas Sel Call (I guess) would allow a call to be set up between the calling and called radios.
Call Type (in Quik-Call II Systems) defines how the radio will react when a valid QCII call is received. In the above screenshot, it's set to Call Alert with Voice: this means that when the radio receives a valid call, it will beep and the squelch will open (see below) allowing the message to be heard.
The squelch will remain open for the duration set by the Auto Reset Timer. This timer will only start counting once the conditions in the Auto-Reset Timer Type are met. In the above screenshot, this is set to Auto Reset without Carrier Override. This means that the Auto-Reset Timer will start counting down as soon as the squelch opens. If it was set to Auto Reset with Carrier Override, the Timer would only start counting when the carrier is lost - potentially the radio would stay unmuted for a long time due to high traffic on the channel.
The Call Format sets how the incoming QCII call shall be sent (i.e. it tells the radio what to expect). It must match the format used by the paging encoder.
Sidetone sets what is played on the speaker when the radio sends a QCII call. I've not played with this setting but I believe when its set to long, the radio will actually play the sent tone pair on the speaker. This setting helps to let the user know when the paging tones have been sent so they known when they can speak.
Pretime is important if the paging tones will be sent via a repeater. Older analogue repeaters often had a longer key-up time (sometimes as much as ~200ms). This delayed key-up could chop off the first few milliseconds of the paging tone and the receiving radio might - as a result - disregard it. In the screenshot, it's set to 500ms: when the user presses send, the radio will transmit the tones but will wait 500ms before sending the first tone.
Limited Patience Timer sets the amount of time the radio will wait for the channel to become clear, before transmitting the QCII tones inpolitely (i.e. transmit them over someone else's transmission).
The Contact List entry basically defines the Contact Name and which tones (the actual frequencies) will be sent as well as on which channel.
The Quik-Call System gets the settings from Quik-Call System - in this case, Sys 1. The Revert Channel and Revert Channel Zone allow you to define which channel the QCII tones should be transmitted on.
The Tone A and Tone B settings define which tone frequencies should be sent. The frequencies correspond to the Tone Code - otherwise known as the Reed Code.
If the channel, on which the QCII tones will be sent, uses PL (CTCSS) or DPL (DCS), you can have that the QCII tones are sent without PL/DPL by ticking Strip PL. This may be useful if the channel is used for both voice and paging.
In the above screenshot, there is s Signalling System setting for both Transmit and Receive. The receive setting defines which signalling system will be used for decode. On analogue channels, this can only be MDC or QCII. Select-5 (ZVEI, CCIR etc.) requires a 5-Tone Channel not available in all models and regions.
The transmit setting will be used when the radio transmits - this could be when the user makes a selective call ( see Sel Call above) or sends a page (see Call Alert above).
The Signalling Squelch setting in the Personality is like a logical condition. If you set it to AND, the radio will require whatever is in the Squelch Type setting and (think logic AND) whatever is in the Signalling System setting to unmute. If you set it to OR, the radio will unmute if either the Squelch Type setting or whatever is in the Signalling System setting are met (i.e. logic OR). The Squelch Type would either be set to PL, DPL or CSQ (carrier squelch).
I have not worked with QCII for about 20 years so much of this is based on experience with other (older) products and systems. Much of the jargon has remained the same so anyone who has worked with QCII in the past can get going quicker.
As always, I've posted this here in the hopes that it may be of use to someone at some point. My head is full of information and, to quote my more famous namesake:
I have not worked with QCII for about 20 years so much of this is based on experience with other (older) products and systems. Much of the jargon has remained the same so anyone who has worked with QCII in the past can get going quicker.
As always, I've posted this here in the hopes that it may be of use to someone at some point. My head is full of information and, to quote my more famous namesake:
I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skillful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.
― Sir Arthur Conan Doyle, A Study in Scarlet
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