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The originating local substation (LS) has now
completed three actions:

1. Generated a seven-second (7.0-second) or

three-second (3.0-second) TTU interval.

2. Unkeyed GUARD for two (2) seconds.

3. Sent a half-second (0.5-second) or two-

second (2.0-second) interval of
TRIP-SHIFT LOW.

19.1.3 Remote Substation Receiver

The remote substation receiver (RS) actions are
shown on the timing diagram in Figure 19-9.
LOW SIGNAL (P1-13) and NOISE (P1-14) are
ANDed together and integrated (1.5 sec/0) in
U6.1 and U4.2 to produce an output on TP9. TP9
output generates a one-second (1.0-second)
sampling pulse at point C. U6.3 and U6.2 are
AND gates. The HIGH input (A) is ANDed with
C, and the LO input (B) is ANDed with C. The
receiver at RS recognized that it had lost carrier
for one-and-a-half (1.5) seconds and is looking for
a half-second (0.5-second) or two-second (2.0-
second) transmission of LOW (TRIP) or GUARD
HIGH.

The TRIP output is on D (U6.2 pin 4), while the
GUARD output is on E (U6.3 pin 10).

19.1.4 Remote Substation Transmitter

From the action described in “19.1.1 TTU Cycle”
above, a trip has been sent from LS, and thus there
is an output from D. LED 1 is illuminated,
signalling receipt of a trip from LS. When the
signal returns to GUARD, there is an output from
E (U6.3 pin 10), and LED 2 is illuminated. This
indicates receipt of GUARD. Output D (Y1)
saturates QN2.1 and causes a TT INITIATE
command in the remote substation (RS). This does
not occur if JU6, 7, 8, and 9 are in position 2 to 3.
Instead, two seconds of trip are sent to the master
unit. QN1.1 (Line C) via JU7 (in positions 2-3)
generates two (2) seconds of TRIP.

Refer to the “REMOTE SEND TRIP 1 – TP7”
portion of the timing diagram for the REMOTE
TRANSMITTER (Figure 19-10).

If Jumpers JU6, JU7, JU8, and JU9 are in the 1-2
positions, the sequence of events in the remote
transmitter is the same as in the local substation:

1. Generates a seven-second (7.0-second)

TTU interval (U9.1 pin 6).

2. Unkeys GUARD for two (2) seconds (U9.2

pin 10).

3. Sends a half-second (0.5-second) interval

of TRIP (TP7 U10.1 pin 6).

19.1.5 Local Substation Receiver

The local substation (LS) receiver responds to the
action of the remote substation (RS) transmitter.
This is shown on the timing diagram “LOCAL
RECEIVER” (Figure 19-12) when jumpers JU6,
JU7, JU8, and JU9 are in the 1-2 positions. The
GUARD signal is turned off in the remote trans-
mitter, and there is an output from U6.2 or U6.3.

As in the RS, NOISE and LOW SIGNAL are
ANDed together and produce a one-second (1.0-
second) sampling pulse at the inputs to AND gates
U6.3 and U6.2. The half-second (0.5 seconds) of
TRIP (low frequency) sent by the RS causes an
output from U6.2 pin 4 through Jumper JU6 to
QN2.1. U9.1 is already set (7 seconds) and is not
changed because of a logic “0” on pin 5. When the
remote transmitter returns to GUARD, U6.3 pin
10 has an output and U6.4 pin 11 has an output
that drives U10/2 pin 12 via JU9. A two-second
(2-second) UNKEY command is sent to the trans-
mitter (see Timing diagram LOCAL XMIT unkey
P1-17 U10.2 pin 10 TP8). After the two-second
(2-second) UNKEY interval, U7.2 pin 10 shifts
the carrier to the HIGH frequency for a half-
second (0.5 seconds) and LED 4, “SEND
TRIP 2,” is illuminated.