Shades of all-tube mobile radios with Dynamotors!
In 1970, I had a GE Pacer under-dash 2-channel mobile radio with a
Secode MTS decoder mounted on its right side, with a PTT handset on the
front. My telephone number was JL-2-6759, the JL indicating which of
the MTS channels I was to monitor. A Pacer was completely tubed, but it
had a transistorized power supply and put out 12 watts.
The Secode decoder was an electromechanical stepper switch that
responded to the 600/1500 Hz tones. When a call to a mobile unit was
being made, the 1500 Hz tone was changed to 600 Hz at a 10 PPS rate.
Each pulse ratcheted the decoder wheel one notch, and pins were placed
at each notch that represented one of the digits of the assigned phone
number. If a pin was at the notch where each pulsing series ended, the
wheel would be latched at that point, ready for the next digit. As each
of the five digits was dialed, the wheel would make it all the way to
the ringing contact. If any of the five digits did not match the pin
placement, the wheel would not be latched and would return to the home
position. Because there were few MTS users in town, I usually knew that
an incoming call was for me, simply by counting the stepping sounds in
my head. In 1970, the move to IMTS had already begun. IMTS used
frequency-agile radios that could place and receive calls automatically.
To place a call, I had to lift the handset and first ensure that nobody
was using the channel. If it was free, I keyed the PTT for two seconds
or so, and waited for the mobile operator to respond. I then gave her
my mobile telephone number and the number I wanted to call. This was
certainly a slow and bothersome way to make a phone call, but hey- this
was in the "early days" of mobile telephone service!
73, Eric Lemmon WB6FLY
Mark Holman wrote:
>
> This sounds like the way the old mobile Radio Telephones used I think was 20
> khz. ( ?? ) tone and the rotary dial, and looking at the control in that
> fashion old RT used the 152-157 MHz. offset I think if I have it right.
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