ZETRON 748, Technical Manual

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Operation
025-9368H 49
Sub-audible Only
To initiate a call using this method requires the Model 748 to receive 3-plus seconds of an enabled
tone/code with Interconnect Gateway enabled. In a two site installation, a four channel radio would
be required. Channels 1 and 3 are the normal dispatch channel for the two sites. Channels 2 and 4
would be used to initiate a Gateway call to the other site. To initiate a Gateway call, switch to
channel 2 and key up for 3-plus seconds and then unkey. The Model 748 will respond by taking a
phone line off-hook, and executing a forced autodial. The originating mobile will hear the beeps
(from dialing) and switch back to channel 1 (normal dispatch channel). Now all mobiles in the user
group will be able to hear the call as it progresses.
When the Model 748 receives 3-plus seconds of an enabled tone/code, it looks to see if that
tone/code also has Interconnect Gateway enabled. If Gateway has been enabled, the Model 748
switches from repeater panel operation to interconnect operation. It takes the user number of
gateway enabled tone/code (from the repeater panel user database) and executes a mobile originated
interconnect call as if that user (from the interconnect user database) has signed-on with DTMF. You
could also think of this as no-DTMF originated interconnect. If tone 103.5 Hz in the repeater panel
user database (User 14) is enabled for Gateway, then when 103.5 Hz has been received for greater
than 3 seconds, the Model 748 will execute the programming for User 14 in the interconnect user
database.
The need to switch channels to place an Interconnect Gateway call is based on using sub-audible to
select the functions instead of DTMF. The channel used to initiate the Gateway call uses a different
decode tone/code (encode in the radio) but will typically use the same encode tone/code (decode in
the radio) as the normal dispatch channel for call setup. When the call switches over from repeater
panel to interconnect, the same encode/decode used for dispatch is used. This allows other radios in
the user group to monitor/participate in the call. It also provides a way for the originating mobile to
hear the progression the call (dialing the phone number) before switching back to the normal
dispatch channel.
Short Sign-on + Sub-audible
To initiate a call using this method requires a single DTMF digit for greater than 500mSec with sub-
audible tone/code. The interconnect user equipment type must also be set to MobileLink. This
method has two advantages over the first. 1) no changing of channels on the radio is required to
setup a call. 2) site selection (in a multi site setup) can be based on a single number and remain
consistent throughout out the system for all user groups.
A four channel DTMF equipped radio can now support four different sites or coverage areas. Each
user group has a single tone/code used for dispatch operation. Each site is assigned a digit which is
used for site selection as a short sign-on digit. To contact other mobiles in your user group on Site-3
from any of the other sites, simply key up and send a DTMF “3” for greater than 500mSec and
unkey. The Model 748 will see a valid mobile originate access, see that the equipment type is set for
MobileLink and perform a gateway call to Site-3. Since short sign-on uses sub-audible to validate
the DTMF digit, all user groups can use the same digit to select the site. The sub-audible used to
separate user groups during dispatch also is used to distinguish them for short sign-on.