Issue 0
1 947993
Shorting
Jumper
HI Z Out
600-OHM
Input
HI Z Out
SHLD
CT
Shorting
Jumper in
Normal
Position
HI Z Out
600-OHM
Input
HI Z Out
Shield
600-OHM Balanced
Line Input
To Aux. Input
of Amplifier
Phono
Plug
Phono
Plug
OR
N
O
R
M
M
I
C
SHLD CT
VMT-1
INPUT MATCHING TRANSFORMER
CONNECTIONS
The VMT-1 matches 500-600 Ohm lines to either
a high impedance input or output of an amplifier.
It may be used to connect audio page ports of
telephone systems to most 70 Volt amplifiers.
The VMT-1 provides an impedance match
between a 500-600 Ohm balanced line and
auxiliary high impedance input or 25 Volt output
of an amplifier.
Figure 1
Connection to an auxiliary input of an amplifier is
made using a standard phono patch cable or
screw terminals. Connection to a 500-600 Ohm
input is made to screw terminals. A shorting
jumper is available when the unit is used to
connect a high impedance output to the
microphone input of an amplifier.
DIMENSIONS/WEIGHT
• 1.75" H x 3.75" W x 1.25" D
(4.45cm H x 9.53cm W x 3.2cm D)
• 0.5 lbs. (.23 kg)
Figure 2 shows the VMT-1 used to
connect a 600 Ohm balanced line to the auxiliary
input of a commercial 70 Volt amplifier. If the
amplifier uses phone jacks for auxiliary input
connections a patch cable with male phono ends
may be used for the connection. Shielded single
conductor wiring is used when the amplifier is
equipped with screw terminal connections.
Figure 2 Input Matching Ttransformer
To connect a 600 Ohm line to a ¼
microphone input of an amplifier move the
shorting jumper to the lower 2 header pins on the
unit. The connection the amplifier may be made
using a standard patch cable with phono plugs
and a ¼” male/phono jack adapter.
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