FRS Rule 3 - Types of communications.
- (a) You may use an FRS unit to conduct two-way voice communications with another person. You may use the FRS unit to transmit one-way communications only to establish communications with another person, send an emergency message, provide traveler assistance, make a voice page, or to conduct a brief test.
- (b) The FRS unit may transmit tones to make contact or to continue communications with a particular FRS unit. If the tone is audible (more than 300 Hertz), it must last no longer than 15 seconds at one time. If the tone is subaudible (300 Hertz or less), it may be transmitted continuously only while you are talking.
- (c) You must not use an FRS unit in connection with any activity which is against federal, state or local law.
- (d) You must, at all times and on all channels, give priority to emergency communication messages concerning the immediate safety of life or the immediate protection of property.
- (e) No FRS unit may be interconnected to the public switched network.
In Family Radio Service Rule three (3) subpart (b) above, the rule states; '' (b) The FRS unit may transmit tones to make contact or to continue communications with a particular FRS unit.'' It continues on to say; ''If the tone is audible (more than 300 Hertz), it must last no longer than 15 seconds at one time.''
In the application that I am writing about here, I have a friend who works with the hearing impaired. She has several students who would like to communicate, but are unable to use the telephone for voice communications. They do have computers. A problem for one of them is that the (single) parent is unable to use the phone when they are on-line via modem. The income of the single parent restricts adding a second line for unstandable (financial) reasons. To enable these two to communicate using their computers, an alternative was to use a low powered (100 mW ERP) FRS radio and a terminal node controller (TNC).
Having read and understood the above rule to; ''allow audible tone bursts of less than 15 second duration at a time, and to transmit tones to make contact or to continue communications with a particular FRS unit.'' I interfaced an MFJ-1270C TNC to the Radio Shack model 21-1804 FRS transceiver.
The 21-1804 is not modified internally in any way. The radio is not changed, nor is any internal setting adjusted. The radio is as ''type accepted.'' Further, no antenna change, or inductive coupling is made. In other words, the radio operation and electronics are not altered in any way. The radio with the Packet tones applied is still within the 2.5 kHz deviations as required elsewhere in the FRS rules.
The external MIC and external earphone/speaker jacks are used to make this combination work. The radio is automatically keyed by the MFJ-1270C TNC when the enter key is pressed, or the PacLEN of 256 characters is reached.
The radio will require that a TXDelay of 30 (300 millisecond) is used, and I set the MAXFrame to one (1) and the FRack to five (5). A Packet length (PacLEN) of 256 takes less than three (3) seconds to transmit, thus the tone ON is below the ''15 seconds at one time'' as required in FRS rule 3, subpart (b).
The RadioShack model 21-1804 audio circuits can easily handle the 1200 baud (audible) packet tones of 1200 and 2200 Hz.
The RadioShack model 21-1804 volume is opened 1/4th turn (from the ON position, set to about 9:00 o'clock).
The two hearing impaired users live about three blocks apart and the radios have sufficient signal to travers the quarter mile span without Packet retries (error).
The drawing below outlines how the RadioShack model 21-1804 is interfaced to the MFJ-1270C terminal node controller.
The FRS channels are as follows:
Channel (MHz)
1. 462.5625
2. 462.5875
3. 462.6125
4. 462.6375
5. 462.6625
6. 462.6875
7. 462.7125
8. 467.5625
9. 467.5875
10. 467.6125
11. 467.6375
12. 467.6625
13. 467.6875
14. 467.7125
No license is required to operate an FRS unit?
WebMaster, Buck Rogers K4ABT "
[email protected]"
© G. E. "Buck" Rogers Sr.
