Isolating Noise Problems - DKS 1812 Owner's Manual

5.3

Isolating Noise Problems

If noise or hum is present on the resident's phone line after installation of the 1812 telephone
intercom system, use the procedure on the next page to find and correct the source of the noise. This
procedure will require the use of a telephone test set (DoorKing p/n 1800-050 or equivalent).
Typically, noise is usually introduced into the system because of incorrect wiring, poor quality of wire,
wire runs exceeding maximum distances, phone and high voltage power wires running in the same
conduit or in very close proximity to each other, a wrong type transformer was substituted, or the
phone lines, power lines or 1812 circuit board is grounded.
1. Place the BYPASS switch in the BYPASS mode (slide switch to right). If noise goes away,
problem is with phone in/out wiring, power wiring, or 1812 unit. Place the BYPASS switch in
the ENTRY SYSTEM mode (slide switch to left) and proceed to step 3. If noise is still present
when switch is in the bypass mode, disconnect C.O. wires and HOUSE wires from bypass
switch. Connect the C.O. wires to the HOUSE wires. If the noise goes away, the bypass
switch is bad and needs to be replaced. If noise is still present, contact the telephone
company for service.
2. Remove all external items connected to the 1812 unit, such as back-up batteries, relay
connections, push button switches, or time clocks. All terminals should be free of any wiring
except terminals 1 and 2 (PHON IN WIRES), terminal 3 (CASE GROUND WIRE), terminals 4
and 5 (PHON OUT WIRES), and terminals 17 and 18 (16 VAC POWER WIRES). If noise is
still present, proceed to step 2. If noise is gone, the source of the noise is one of the external
devices that were connected to the 1812. Reconnect them one at a time until you find the
item that is the source of the noise.
3. Remove the PHON OUT wires from terminals 4 and 5 at the 1812 unit. Connect your handy
phone directly to the loose PHON OUT wires. The wires should be dead and you should not
have any dial tone on these wires. If you do have dial tone, the 1812 is wired incorrectly.
Disconnect power immediately and refer to the wiring information section in this manual.
4. Disconnect your handy phone from the PHON OUT wires (step 3). Remove the PHON IN
wires from terminals 1 and 2 at the 1812 unit. Connect the PHON IN wires to the PHON OUT
wires. This completely disconnects the 1812 unit from the circuit. Check the phones in the
house. If the noise is gone, problem is with or in the 1812 unit, or with the power supply or
power wiring. Reconnect the PHON IN wires to terminals 1 and 2, and the PHON OUT wires
to terminals 4 and 5, then proceed to step 5. If the noise is still present, problem is with the
PHON IN or PHON OUT wires running from the 1812 unit to the bypass switch. These wires
will need to be replaced and/or re-routed to correct the problem.
5. Disconnect the 16 VAC wires from terminals 17 and 18. If the phone line is now clear, the
problem is in the 16 VAC power run. Check the power lines for a ground, or running next to
high voltage wires, or an improper wire size and insulation, or too long of a wire run. If noise
is still present, go to step 6.
6. If noise is still present at this step in the trouble shooting sequence, this would indicate a
short to ground internally in the 1812 unit. Remove the 8-pin front panel terminal strip from
the circuit board, and check for noise again. If noise is gone, this would indicate a problem
with the microphone board, speaker, push button, or lights on the front panel assembly.
Check for any shorts to ground on any of these components or wiring. Check to be sure that
none of the wires are pinched. If noise is still present, check the wires entering the back of
the 1812 box and be sure that none are pinched. Be sure that these wires are not touching
the back of the 1812 circuit board, possibly causing a short to ground. If all of the above
steps fail to identify the source of noise, contact DoorKing for additional assistance.
1812-162-B-6-09 Page 55