Radio Shack Simplex Repeater Controller (19-345)
© Brooke Clarke 2000 - 2007
Conversion for use with Military radios with U-229 Connectors
This product may not longer be offered by Radio Shack. For info
on Simplex Repeaters see the Simplex
Repeater web page and there's also a Yahoo Group for them.
This unit is made up of a 30 second digital voice recorder and some
to turn on the recorder when audio is present and to play back the
when the audio stops. By connecting to a single
the combination becomes a Simplex Repeater.
The interface to the radio consists of only three wires:
It is not clear to me how this keys the transmit function in a Family
Service (FRS) for which this unit was designed. Although I
have heard that it will work with the Radio Shack 2 meter radios.
In order to get it to work with the PRC-68B and PRC-126 I added a
K Ohm resistor (RS 271-1330) and a 2N2222A (RS276-2009) transistor plus
a cable with a U-183 AUDIO connector. A standard U-229 type cable
could be used since the center pin is not functional in this
The cable was from eBay and is sold as a KG-99 to PRC-104 Crypto-Audio
cable. The 26 pin connector (MS3126E16-26P) was wired with the
letters matching the pin letters on the UG-183 (A to A...F to F).
It is wired as follows:
By wiring the AUDIO E wire to the external power supply pin on the
the external 12 VDC power adapter (RS-273-1662 w/ + to tip) will also
the PRC-126 or PRC-68B radio but NOT the PRC-68. The 19-345
may control the PRC-68 and supply power if the switch on the PRC-68 is
set to OFF! In this position the radio runs from the AUDIO pin E
power supply. The 300 mA transformer shown n this page does not
enough current to drive the 19-345 and the PRC-68 so a 500 mA wall wart
- AUDIO A = Black = Ground = printed circuit board ground
- AUDIO B = Red = Earphone = solder pad for ear
- AUDIO C = Orange = PUSH TO TALK = collector of 2N2222A
- AUDIO D = Blue = Microphone = solder pad for mic
- AUDIO E = Green = External Power = center solder pad next to
- AUDIO F = White = FILL = not used here
- no connection = Brown = no connection
Note that the volume control of the RT being used as the repeater
be adjusted for best sound quality. If it is set all the way down
the 19-345 will not hear the audio.
Photo of component side of stock
circuit board showing the voice chip and what may be an 8 pin PIC
Pin 3 on the microcontroller is the high = play pin.
Here is another way to make the conversion to mil radio use by Federico
Torres, KP4KSL Annotated Photo.bmp
Range Extender -
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