GAI-Tronics MRTI 2000 (No. PL1877A) Microprocessor Radio Telephone Interconnect Installation & Service Manual - Manual (Page 21)

PL1877A Microprocessor Radio Telephone Interconnect Installation
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Off Hook Status of an Attendant Phone - If the LED is lit, the attendant phone is off-hook. If the LED
is not lit the attendant phone is on-hook.
Ring Voltage - If the LED is flashing, ringing is present, if the LED is not lit the phone line is idle.
Phone Line Current Polarity - If the Negative Polarity Indicator is lit, the current is negative. If the
Positive Polarity Indicator is lit, the current is positive. If neither indicator is lit, no current is being
detected.
Ring Threshold Setting - Pressing the UP button increments the ring threshold setting (to a maximum of
7). Pressing the DOWN button decrements the ring threshold setting (to a minimum of 0).
Off-hook Voltage Threshold Adjustment
If parameter 163 is set to 2, you can manually adjust the PL1877A’s off-hook voltage threshold from ±48
V to ±6 V through Test 6. To accomplish this, press the
DOWN and PATCH ON/OFF buttons
simultaneously while the PL1877A is in Test 6. The PWR LED should begin flashing, indicating that the
PL1877A has entered the off-hook adjustment. The remaining LEDs display a binary representation of
the voltage currently on the phone line (maximum displayed voltage = 51 V).
1. Disconnect the PL1877A from the phone line.
2. Set an external dc power supply to the maximum voltage that the PL1877A should recognize as off-
hook.
3. Connect this voltage across the PL1877A’s TIP and RING (P404 pins 2, 3).
4. Press the DOWN and PATCH ON/OFF buttons simultaneously. The PL1877A samples the voltage
and stores it as the new off-hook threshold, and then returns to the normal operation of Test 6.
To abandon the off-hook adjustment without changing the current threshold, press the UP and PATCH
ON/OFF buttons simultaneously while the PWR LED is flashing. The new off-hook threshold does not
change unless the value of parameter 163 is changed or the threshold is again modified through Test 6.
Test 7 – Active Line Swap
If the PL1877A is equipped with the second line option, the phone line used for all other tests may be
selected by pressing the
UP button. A DTMF “#” is routed out the active phone line. The least two
significant LEDs (refer to the LED assignment diagram on page 13) give a binary indication of the phone
line selected.
Test 8 – Network Tone Decoding
This test accesses the phone line and the three most significant LEDs (refer to the LED assignment
diagram on page 13) indicate the detection of:
• Dial Tone - When dial tone is detected, LED 1 (the most significant LED, bit 7) lights.
• Busy Tone - When busy tone is detected, LED 3 lights.