Sigtronics S-A-F-E Installation Instructions Instrukcja Użytkownika Pobierz pdf (Strona 7)

If all works ne, skip down to “Electrical Noise Test” on this.

If anything does not work as above, you have one of three

possible PTT switch wiring errors:

1. PTT line (white/red or white/blue wires) open or not

connected between a PTT switch and the SAFE unit.

2. Open or missing return line (black wire) to a PTT switch.

3. Reversed PTT lines. Ocer 1’s PTT line connected to Ocer

2’s PTT switch and visa versa.

Electrical Noise Test

The last thing to do before the radios are hooked up to the

unit is a simple noise test to verify system wiring as well as

vehicle electrical system integrity.

1. Unplug all intercom headsets except for the drivers.

2. Make sure all the SAFE panel controls and switches are set

as in “System Setup” on page 6.

3. Start the vehicles engine and let it idle a bit. This is a

stationary test - the vehicle should not be moving and

should be in “PARK” or “NEUTRAL” with brakes set.

4. Close all vehicle windows and doors to eliminate as much

background noise as possible.

5. Turn on as much vehicle electrical equipment as possible.

This usually means all lights and strobes. Do not turn on

sirens or horns.

6. Put on the driver’s headset and make sure the headset

volume control is set to maximum.

7. With the vehicle still in “PARK” or “NEUTRAL” and brakes

set, slowly increase the vehicle engine rpm from idle to

about 1500 RPM and back again. While doing this, listen

for any whine or hum in the headsets. Except for some

possible engine background noise being picked up

from the headset microphone you should not hear any

“Electrical” whine or hum in the headset.

8. Shut o the vehicle engine as well as the lights, strobes,

etc. If, while the engine was running, there was no

electrical noise, skip down to “Radio Hook Up”. If you did

hear electrical noise, use the following to track down the

problem:

Finding The Source of Electrical Noise

Turn the vehicle power o and disconnect the SAFE ground

connection (green wire) from ground. Turn on the vehicle

power (engine o), put on the driver’s headset and see if the

intercom part of the SAFE unit is working.

If You Can Hear Yourself In The Headset:

1. Then the SAFE intercom return wire (black) is incorrectly

grounded to the vehicle chassis. Look for:

a) A headset jack barrel touching the vehicle chassis.

Most common when a headset jack is mounted directly

into the vehicle’s panel without using the supplied

insulating washers or incorrectly installing the washers.

b) The black wire pinched or cut and shorting to the

vehicle chassis. This can be anywhere along the

intercom wiring as the black wire goes to all headset

jacks and PTT switches.

2. Once the problem has been found and xed, again

make sure that the intercom now does not work with the

green wire disconnected. You could have the black wire

grounded in more than one spot.

3. The next step is to reconnect the green wire and do the

electrical noise test again to assure that you have xed all

possible noise problems.

If You Cannot Hear Yourself In The Headset:

The intercom wiring is correct, but excessive electrical noise

from the vehicle’s power system is aecting the SAFE unit

operation. This noise is getting into the unit on the SAFE

power wires (red and green). There are basically two types

of power line electrical noise sources:

1. Noise generated directly by the vehicle’s electrical/

charging system - most commonly known as alternator

whine. This is only present when the vehicle’s engine

is running and recognized by the fact that the pitch or

frequency of the whine changes directly with the change

in engine rpm. (Higher frequency at higher engine rpm’s

and lower frequency at lower rpm’s.)

The preferred way to solve this type of problem is to have

the vehicle’s electrical/charging system serviced. The

most common cause of this type of noise is bad diodes

in the vehicle’s alternator. Other possible causes are:

Bad vehicle voltage regulator; Bad alternator or battery

cable connections; Missing or bad engine or alternator

grounding straps.

If servicing the vehicle’s charging system is impractical,

installing a good alternator whine power line lter

between the vehicle power and the SAFE red wire will

usually accomplish the same thing. Do not use the type

of lter that installs on or near the alternator. NOTE: This

solution should not be considered a permanent x. Vehicle

charging system problems of this type will eventually

cause other equipment failure as well as shorten the life

of the vehicle’s batteries.

2. The other type of noise is that generated by equipment

that uses the vehicle’s power. This type of noise is usually

constant and does not vary with engine rpm. It does,

however, go away completely if the oending equipment

is shut o or disconnected. Electrical motors in fans or light

bars with rotating lights are two common examples.

Several things can be done to rectify this type of electrical

noise:

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