GAI-Tronics Associated with 600-ohm systems Extended Range Page/Party System Manual - Manual (Page 2)

Pub. 42004-324A
Extended Range Page/Party
®
Systems Page: 2 of 10
\\s_eng\gtcproddocs\standard ioms - current release\42004 instr. manuals\42004-324a.doc
4/00
The cable described above includes conductors to supply ac operating power to each station. All stations
operate from a common power source, enhancing reliability, particularly if no other ac load is placed on the
circuit, or branch line feeding the system. This configuration also allows easy transfer to a back-up power
source in the event of power failure. However, if preferred, each station may be individually powered from
a nearby nominal 120 volt, 50 or 60 Hz single-phase outlet.
Installation Procedure
STEP 1 — Electrical Noise Considerations
When planning your system, consider the following suggestions to avoid electrical noise caused by slip
rings and silicon control rectifier (SCR) power supplies.
Slip Rings - Use a Radio Frequency (RF) alternative and avoid using slip rings as audio conductors. Slip
rings are a source of electrical noise and are not reliable.
SCR Power Supplies - The Page/Party
®
system will be installed in areas where SCR power supplies are
used to power motors or other heavy equipment, consider using one or all of the following four
recommendations to reduce electrical noise.
1. Separation—Locate the Page/ system cables as far as possible from the SCR power supply input or
output cables. Electrical coupling between cables is reduced by the square of the distance between the
cables.
2. Shielding—Use shielded (Armored) system cables if the cable must be run in the same bundle or cable
tray with the SCR power supply cables. Shielded cables reduce capacitive coupling between SCR
power supply cables and Page/Party
® audio cables.
3. Isolation—Two methods of power source isolation can be used to avoid electrical noise:
A. Use a low capacitance (primary to secondary) isolation transformer between the Page/Party ® system
and the ac supply to the SCRs. This will electrically isolate the Page/Party
®
system’s ac power from
the noise generated by the SCR on the ac power feed. Also use an isolation transformer to isolate the
Page/Party
® ac power from an ungrounded ac power source. Note: The neutral side of the transformer
output must be grounded in all instances.
The size of the isolation transformer should be based on the number of amplifiers used in the system.
If 10 or less amplifiers are used in the system, a 500 VA transformer is sufficient. If 11 to 20
amplifiers are used in the system, select a 1000 VA transformer. For systems with more than 20
amplifiers, the transformer should be sized to accommodate a load of 50 VA per amplifier.
B. A battery-powered 24 V dc Page/Party
®
system can be used as an alternative to the standard 120 V ac
system. In this instance, the battery/battery charger provides isolation from the SCR noise on ac power
systems. Cable shielding and separation as mentioned above still apply.
Note: Avoid battery chargers that utilize SCRs in their design.