Specifications

CTCSS served the industry well, and eventually scanner users wanted this feature on their scanners. Eventually it became a
standard feature on higher end scanners.
As the radio bands became more crowded the few dozen CTCSS tones became inadequate and a new method of achieving
the same results was developed. Motorola called it Digital PL (DPL) and the industry name was called DCS for Digital
Coded Squelch. These are continuous digital words transmitted in a similar fashion to CTCSS. They are expressed in a three
digit number, and there are about 100 codes in common use. Some references express DCS codes as Dxxx (D023, D251 etc.)
but the PSR310 only displays the 3 numbers.
What can you use CTCSS or DCS codes for? Well, pretty much the same reasons they are used in the field. The most
common use is to screen out unwanted radio traffic, either on repeaters or on simplex (non-repeater) channels. Is the same
fire frequency in your area also used in the next county? Figure out the code used by your local agency and program it in to
your scanner to exclude the other unwanted users of the same frequency.
Some agencies also use multiple codes to separate traffic on multi-site repeater systems to avoid interference and expensive
steering equipment systems while only needing a single channel. On one system in my area, there is one code used for
operations and another used only to contact emergency services, so the 9-1-1 Center does not need to listen to the day-to-day
operations. You need help, you use the emergency code. This allows a single channel to be used but keeps the 9-1-1 Center
from having to pick out emergency requests from the routine communications.
How do I find these codes?
How do you figure out what CTCSS or DCS codes are used in your area? Well, there are a couple ways. You can find them
yourself by using the Tone Search feature on your scanner, you could look them up on RadioReference or another source, or
you could ask the users if they could tell you. Chances are the third option would be laughed at by the local users, if they had
any idea what you were talking about so the first two options are more realistic.
To have the radio decode the code for you program the Squelch type to “Search”. Once you find the correct tone change the
type to CTCSS or DCS as appropriate and enter in the proper code.
RadioReference.com and other websites will often already have the proper codes listed so a little research may be all you
need. If you use the RadioReference Programming feature of your software package there is a good chance the proper code
will already be there.
Searching and Sweeping
All scanners allow you to search between a set of frequencies in order to find new (to you at least) channels. Some, including
the PSR310, also have preset search protocols, called Service Search, which scan thru a set of commonly used channels for
specific types. The PSR310 has a limited set of Service Searches that include a generic “Public Safety” group, Aircraft,
Marine, Ham Radio, CB and a group of miscellaneous radio channels called FRS/GMRS/MURS/DOT. This last group is
often used by families, small businesses and others for low power local communications.
Surprisingly GRE did not include any type of Service Search for racing operations, race fans are among the biggest buyers of
scanners. The generic nature of the Public Safety Service Search reflects the modern use of many of these channels by
different types of agencies. Gone are the days of segregated Police, Fire, Conservation, Highway and Special Emergency
allocations, now all the frequencies are in a single pool that has reduced the segregation of use. Uniden has a more extensive
list of service search options.
Service Searches (“SRVC”) are entered into a Scan List just like any other Scannable Object. The Service Search frequencies
themselves are not editable by the user but you can lock out freqs when scanning a Service Search.
The GRE also has the standard Limit Search that allows you to search all channels between a pair of frequencies. You can
also lock out frequencies in Limit Searches.
Spectrum Sweeper is a nearfield frequency detector that allows you to find nearby transmitters. There are a couple different
modes. All-Band allows you to search all frequencies the radio is capable of while the Public Safety Mode allows you to