Thomas & Betts DH720 Instruction Manual
1
Enclosed you will find:
• Indoor Speaker • Wire Labels • Wire Nuts • Wall Anchors
• Outdoor Speaker • Transformer • Pull Cord • Screws
INSTALLATION
Replacement for Existing Chime
1. Locate Indoor Speaker where chime is located. In many cases
existing wiring can be used–see enclosed “Identifying Chime Wiring.”
2. If existing Chime is mounted at a height which is inconvenient to
reach, a pull cord is provided to operate the intercom control button.
3. Important: Do not locate speakers more than 500 feet apart. Do not
locate speakers back-to-back on the same wall.
4. Locate Outdoor Speaker where existing pushbutton is located. Use
pushbutton wiring–see enclosed “Identifying Chime Wiring.” Note: If
existing pushbutton is uneven or narrow surface, it will be necessary
to locate Outdoor Speaker elsewhere.
5. Install Outdoor Speaker: (A) on an even surface; (B) on a surface wide
enough for the speaker; (C) as close to existing wiring as possible.
Caution:
• Turn off house power at the source and leave it off until installation is
complete.
• All wiring must comply with local wiring codes.
New Installation Location
1. Install the Indoor Speaker at an easy operating location.
2. Install the Outdoor Speaker close to the door and at an easy
operating position.
3. Try to install speakers where running the wiring will not present a
problem. Avoid running the speaker wire next to any AC power
wires.
New Installation
1. Install a 16-volt transformer (Carlon Model DH905). Mount the
transformer to a junction box or a circuit breaker box. Do not mount
transformer in high temperature area (i.e., attic). Follow transformer
installation instructions. Connect primary side of the transformer to
120V AC.
2. Run standard 20 AWG (DH965) bell/chime wire from transformer’s
secondary terminals to the Indoor Speaker location.
3. Run standard bell/chime wire from the Outdoor Speaker location to
the Indoor Speaker location.
4. Connect brown Outdoor Speaker wires to green Indoor Speaker
wires shown in Figure 1.
5. Connect transformer wires to red Indoor Speaker wires as shown in
Figure 1.
6. Use wire nuts to make all connections. Insulate all connections with
electrical tape.
7. If electric door strike feature is required, see “Optional Electric Door
Strike Wiring.”
INSTRUCTION GUIDE
Door Chime Intercom DH720
Congratulations on a wise purchase!
Indoor Speaker
Outdoor
Speaker
Transformer
Green Wires Red Wires
120V AC
Primary
Brown
Wires
Figure 1
16V
2
Identify the existing wiring by determining whether the common wire connection is at the transformer location
or at the chime location. Follow the instructions and diagrams for identifying the individual wires.
When wiring has been identified and labeled, proceed to installation instructions.
Chime
Front
Trans
Trans Trans
Rear
1. Disconnect the 3 common wires. 2. Touch each wire, one at a time, to the
chime’s FRONT terminal. The wire that
causes the chime to sound is the
TRANSFORMER wire. Label the wire TRANS.
3. One at a time, connect the remaining
wires to the wire labeled TRANS. Then,
operate the FRONT pushbutton. The wire
that causes the chime to sound, label
FRONT. Confirm that the other wire
operates the rear pushbutton. Label the
wire REAR.
4. Proceed to installation instructions.
1. Disconnect the two common wires located
on transformer screw terminal.
2. Connect one common wire to the
transformer terminal and press the FRONT
pushbutton. If wire operates the chime,
label the wire FRONT. If not, connect other
wire; and label wire FRONT.
3. Reconnect the REAR wire to the
transformer terminal. (The FRONT wire
can be used for connection to the
Door Speaker.)
Wiring #1: Front and rear door pushbuttons - Common wire connection at chime
Wiring #2: Front and rear door pushbuttons - Common wire connection at transformer
4. Disconnect the wires from the REAR pushbutton and
connect them together. This wiring will be used as a
second TRANSFORMER wire for connection to the Indoor
Speaker.
Note: The rear button wire can not be used; therefore, the
rear button will not operate intercom. If rear button is
removed, fill hole with appropriate material.
5. Now, it will be necessary to run wiring from the Outdoor
Speaker to the Indoor Speaker. Proceed to installation
instructions.
HOW TO IDENTIFY EXISTING CHIME WIRING
Common Wires
Front
Rear
Chime
Front
Trans
Trans
Rear
Common
Wires
Front
Rear
Chime
Front
Trans
Rear
Common
Wires
Front
Rear
Trans
Chime
Front
Trans
Rear
Front
Wire
Front
Rear
Trans
Wire
Chime
Front
Trans
Trans
Rear
Common
Wires
Front
Rear
Chime
Front
Trans
Trans
Rear
Front
Rear
Front
Wire
Chime
Front
Trans
Trans
Rear
Front
Rear
Rear
Pushbutton
Wires
16V
120V
AC
120V
AC
120V
AC
120V
AC
120V
AC
120V
AC
120V AC
16V 16V
16V 16V 16V
16V
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