Shunt Mode Operation; Shunt Mode Installation - Hitachi ATT-20 Installation, Operation, Troubleshooting

2.7. Shunt Mode Operation

When using the shunt track circuit configuration, do not
repeat the use of the same frequency unless circuits are
isolated by at least two (2) insulated points.
Where less ring-by is desired, keep the track circuit length to
a minimum and use the shortest possible track leads. Refer
to Figure 2-1 and Table 2-2 for shunt track circuit application.

2.7.1. Shunt Mode Installation

Refer to Figure 2-1 and proceed as follows to install the ATT-20 in shunt mode
application:
1. Connect transmitter terminals 3 and 4 to terminals 3 and 4 of the USS-21 surge
suppressor. Continue the cabling to the track from terminals 1 and 2 of the
USSP-21. Repeat the above procedure for cabling receiver input terminals 5 and
6 to the rails. All transmitter and receiver cables must be #9 AWG or heavier and
used as a twisted pair. Ensure the combined lengths of the transmitter and
receiver cables do not exceed 500 ft. Also, do not exceed block lengths of 300 ft.
2. Connect terminals 7 (relay +) and 8 (relay -) to the relay. The recommended relay
to be used with the ATT-20 is a PN-150B, 400 ohm plug-in type, STS USA Part
No.: N322500-701.
3. If the ATT-20 is to receive its DC power from a battery or constant potential
rectifier supply (CPR) or an electronically regulated supply, a surge ripple filter
(Part No. N451590-0301) must be used as follows:
a. Connect terminals 1 (+) and 2 (-) of the ATT-20 to respective "+DC" and "-
DC" terminals of the ripple
b. Jumper terminals 2 to N on the ripple
and N (negative) to their respective battery bus or supply terminals. Lightning
arrestor USG-A N451552-0101 should be across ripple
N. Refer to Section 5 for the details on lightning protection.
4. If the ATT-20 is to be powered from an electronic supply, this supply should be
capable of delivering 1.0 ampere at 12 VDC (on the ATT-20 side of the surge
ripple and be dedicated to the ATT-20 that it is powering.
filter)
Copyright 2019
CAUTION
Figure 2-3
filter. See
filter
SM 6299 Rev. 3, March 2019
ATT-20 Audio Track Transceiver
.
and cable terminals B (positive)
terminals B and
filter
2-4