Figure 1.
Telephone:
Connect telephone wires to the input screw terminals marked TIP and RING. For connection to unused CO trunk port, see
Figure 4. For connection to CO line, Centrex line, or Analog Station port, a Wheelock TPI-100 is required.
Microphone:
Connect balanced low-impedance microphone wires to the input screw terminals marked LO-Z. The shield must be connected
to the GND screw terminals. An unbalanced microphone may be connected to either one of the LO-Z screw terminals and GND.
CAUTION:
To avoid possible interference, the microphone input cable must be a shielded cable with the shield connected to GND.
Music:
To connect an FM tuner, CD player or cassette to the MUSIC/HI-Z input jack, use a single conductor shielded cable terminated
in a standard RCA type phono plug.
OUTPUT CONNECTIONS:
(See Figure 2.)
Figure 2.
Connect output wires to the COM screw terminal and the selected mode for constant voltage distribution, i.e. 25V or 70V. The constant voltage
distribution method facilitates the use of multiple speakers in parallel with a single amplifier. Note that each speaker must have its own line-matching
transformer. The tap on the line matching transformer is selected to give the power desired for each speaker.
It is recommended for long distances to use a wire as heavy as possible in order to minimize a consequent power loss on the distribution line.
NOTE:
To allow for future expansion. It is recommended that the total system wattage requirement should not exceed 85% of the amplifiers rated output
(i.e. 17 watts for the TPA-20 and 30 watts for the TPA-35) the total system wattage requirement is the summation of the wattage tap selections of all
system speakers and horns.
A single 8 ohm speaker may be connected to the COM and 8 ohm screw terminals. Be sure that the wattage rating of the speaker exceeds that of the
amplifier, i.e. 25 watts or higher for the TPA-20 and 40 watts or higher for the TPA-35.
CONNECTING AMPLIFIERS IN SERIES:
(See Figure 3.)
In some instances where an expansion of the listening area would necessitate a number of speakers that would exceed the maximum recommended
quantity, two amplifiers may be connected in series. This hook-up will in effect double the output power (i.e. 40 watts for two TPA-20 and 70 watts for
two TPA-35) for a 25V constant voltage system.
The input wires must be arranged to parallel the inputs of the two amplifiers, and the volume and tone controls of both amplifiers must be at the same
setting to assure that each amplifier will share the load equally.
Figure 3.
P81782 G
Sheet 2 of 4
PLUGGING IN UNIT TO 120 VAC:
The TPA amplifiers have no power on/off switch. Before plugging in the AC cord to 120 VAC, make sure that all connections are proper and that the
front panel controls marked PAGE and MUSIC are turned to minimum (counterclockwise).
UNUSED CO TRUNK PORT CONNECTIONS:
(See Figure 4.)