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

2.7.2. Shunt Mode Adjustment

Proceed as follows to adjust the ATT-20 in a shunt mode installation:
1. Connect a hard-wire shunt across the rails outside of the defined block at the
desired ring-by distance from the ATT-20 receiver track connections (terminals 5
and 6). Table 2-2 shows typical ring-by parameters for 3.0 ohm/1000 ft. ballast
and 0.1 ohm adjustment shunt.
The adjustment shunt mentioned below is not a hard-wire
shunt.
accurately represent the desired shunting sensitivity.
2. Adjust the ATT-20 transmitter output level through the access hole in the top
cover until the relay is energizes.
3. Remove the hard-wire shunt from the rails.
4. Place an adjustment shunt across the rails at the receiver connection (not the
ring-by distance). The relay should deenergize. A compromise between the
shunting sensitivity (adjustment shunt) and ring-by distance will be achieved per
application.
5. Remove the adjustment shunt from the rails. The adjustment procedure is
complete.
Table 2-2.
Track Length
(Ft.)
100
200
300

2.8. Series Mode Operation

Series track circuit locations operating at the same frequency must be separated by at
least two insulated joints. A typical series mode application would be at a switch lock.
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Note
The resistance of the adjustment shunt must
Ring-by Parameters for 0.1 Ohm Shunting
Total Cable
Length (Ft.)
12.28 KHZ
100 11
300 14
500 19
200 18
300 21
500 29
300 30
400 35
500 40
SM 6299 Rev. 3, March 2019
ATT-20 Audio Track Transceiver
Typical Minimum Ring-By (Ft.)
15.0 KHz
10
14
19
18
21
29
30
36
43
20.0 KHz
9
13
19
17
22
33
33
41
52
2-5