How is it all Linked?


All of the sites (with the exception of Kaneohe) are linked using carrier grade 4 wire audio circuits (4-wire E&M) over a statewide digital microwave radio system. Voice encoding on these channels uses high quality 64kb/s uLaw encoding.

4 wire cards (model VF-5C) are interfaced via Intraplex servers interconnected over T1 circuits. Due to the nature of the synchronous network, there is virtually no voice delay throughout the system.

Kaneohe's link is provided by dedicated radio-over-IP (ROIP) boxes (Telex IP-223) which are connected via carrier grade private IP from Round Top to Kaneohe. Because it is IP, this link does exhibit a voice delay.

The link from Volcano is done over IP using Allstarlink and BeagleBone Black hardware.

* NOTE: One of the nuances of this system is the use of site-unique courtesy tones. You can tell what site a user is talking on by listening to the beep sequence after the user unkeys. If you make it a point to learn all the tones on the system, you'll be able to instantly tell where they are talking in from.



Quantars use a legacy synchronous serial protocol at 9600 bps for linking. Since we have more than 2 Quantars, there is a central comparator which all the repeaters link back to. This results in a star network topology with Roundtop being the hub.

The synchronous serial (V.24) links are carried through the same backbone T1 circuits and digital microwave as the analog, except a different Intraplex card (DS-961DG) is used at each end.

For the Kaneohe and Volcano sites, old Cisco 2651XM routers using the L2TPV3 protocol to transport the V.24 synchronous serial over IP back to the Roundtop comparator.


Finally, there is a growing global network of P25 repeaters (all Quantars thus far) called P25NX which the XO system is connected to. P25NX is still in its first phase which uses Cisco routers and the STUN protocol to a central server which interconnects all the individual repeaters. Please see our Operating P25 on XOnet Page.

Last Updated April 12, 2016