During the '70s, I became aware of some of the hardships of using the telephone experienced by folks who are hearing or speech impaired. Some devices such as surplus mechanical TTYs were being offered but they were awkward, not portable and required a unit at each end of the phone line. Tone dialing was nearly universal in the U.S. and it seemed to me that there must be a simpler and better way for these people to communicate. Because the DTMF chips were not yet available, I started to design a system using discrete parts. My concept proved workable though the units were bulky and soon, the tone I-Cs were plentiful, bringing "Tone Writer" to fruition.

The "Tone Writer" concept is as follows: to make the complete alphabet, including numbers and some punctuation marks, multiple keystrokes were needed. A convenient dial combination requires pressing two keys---the first corresponding to the prefix letters on the number key, and a second to do an "enter" based on the position of the prefix letter. 7, 8 & 9  were chosen for the letter "enter" keys and 0 for the numbers.  Example: to print an "A" press "2" then "7"---"A" and "7" being in the first position to the left . For "B" press "2" then "8"---"B" and "8" are in the middle position. The number "5" would be "5" then "0".

The "Tone Writer" is a handheld and a battery powered appliance which is connected to the telephone at the earpiece via a suction cupped pickup coil. Red and green level lights are used to indicate the quality of the signal from the phone line and the message screen is an LCD alphanumeric display. The above top left picture is an early model using an LED screen. The second picture is of an improved, LCD display model.  In time, there was a need for a keyboard to take the "work" from the multiple keystrokes. The center picture is of a "Tone Writer" and a Keyboard combination. 
 

The Tone Writer Keyboard sequencing concept was applied to data acquisition and control. Pictured at the left is a unit that was used to remote log and control analog and digital data of a reverse osmosis water purification system.  Onboard is an LCD screen, a step counter and a small keypad to locally select and monitor the various functions. The sensor and phone connections are made on the terminal strip at the right-hand edge of the unit.

To log data, a technician would dial a phone number of a site using a standard tone phone. Upon answering, a function would be selected by pressing an appropriate number on telephone. Example: '1' for temperature, '2' for pressure, etc. then star and the reading from the site is sent via the phone line to a "Tone Writer" attached to the phone. The result is a simple, low cost, data logging system that can be accessed from any tone phone. No computer or modem required!

Of course, to develop, test, and troubleshoot a DTMF system, some kind of tone generator is needed. The pictures at top right are of two devices that I use. The far right is the easiest to fabricate since the tone generation is done by a low cost telephone. (The one pictured is a "freebee" promotional give away.) The interface consists of a coupling transformer, a 600 Ohm resistor, two .1 mfd capacitors, two RJ-11 sockets and a dc power connection  mounted on a perfboard. The second from right is a unit using a keypad, a DTMF integrated circuit and a burst crystal to generate the tones built into a "black box".  Either a "wall wart" or a 9 Volt battery can be the power source.
 

At the left is a picture of the phone patch which I used to control my 2 Meter Ham rig  by phone line when I was away from my QTH---and, later it was used to remotely operate my SSTV security system. To work the radio or the slow scan TV, my QTH phone number  is dialed. The ring is detected to "answer" or "pick" the phone line; a security code is entered to open for dialog; then "star" is pressed to turn on power;  a"7" for transmit; an"8" to receive. For images, a"6" is pressed to capture a picture; a"5" to send the picture; a"2" for camera automatic; and a "pound" for disconnect. Backup timers and a dial tone detect are also aboard to prevent accidental line capture and busy lockup.