2000-11-08 CC - Laserfiche WebLink

Home Browse Search

radio coverage must be improved so that it is closer to the coverage from the primary base stations. 2.6 COMMUNICATIONS FACILITIES BETWEEN DISPATCH CENTER AND THE RADIO SITES There are communications facilities to interconnect the dispatch center in Anoka and the various base radio sites and receiver sites. At the present time, those communications facilities are leased telephone lines from Qwest Communications. Almost all of the base radio stations are . controlled by DC signalling which requires a copper connection type telephone line between the dispatch center and the radio sites. It is becoming very difficult, and in some cases impossible, to obtain DC lines from the telephone company and, therefore, some additional electronic equipment must be added on both ends of the telephone line to cause the line to look like a DC line when it is in fact a different kind of telephone company lines. DC signalling has never been as reliable as the more modem in-band tone signalling to control the remote radio base stations at the radio sites from the dispatch center. The addition of the electronic devices to cause the line to simulate a DC line has compounded those control problems. The Anoka County radio technical staff has been experiencing difficulties in trying to keep the control of the base stations functioning as the problems with DC control are compounded. The best solution to this problem would be to replace the telephone lines with microwave facilities. Microwave is very reliable and functions extremely well and reliably. An alternative is to purchase new base radio equipment that operates with in-band tone signalling rather than with DC signalling. The existing base radio stations are generally more than ten years old and should be candidates for replacement in the next few years. Therefore, if the decision is made to continue use of the VHF radio band, one of the considerations must be replacement of all of the DC control stations at as early a date as possible to reduce the problems with station control over telephone lines. The best solution will be to use microwave facilities to control the stations wherever it is economically feasible. 2.7 STATUS OF ANTENNAS AND TRANSMISSION LINES Most of the antennas and transmission lines are about 25 years old, dating from the days when LEAA funding was available in the middle 1970s. Those lines and antennas have reached the end of their useful life and should not continue in service for critical public safety radio systems where high system reliability is required. 2.8 BACK-UP POWER The only sites in the Anoka County public safety radio systems that have backup electrical power are the Anoka County Government Center and the Andover site where the County radio maintenance facilities are located. At all other sites, if commercial power fails, the radio stations will shut down and stay down until commercial power is again available. In some cases, it may Ronald Vegemast Engineering, Inc. -18- Report: Anoka County