GAI-Tronics MRTI 2000 (No. PL1877A) Microprocessor Radio Telephone Interconnect Installation & Service Manual - Manual (Page 136)

Paging PL1877A Microprocessor Radio Telephone Interconnect
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If no digits were required from the operator (programming the number of 2-Tone digits accepted from the
user on the selected channel to 0) both the A and B tone frequencies would be predetermined through
programming and the same tone sequence would be sent every time a 2-Tone page is generated on this
particular channel.
Group Call
A group call occurs when both tones of a 2-Tone paging sequence are the same frequency. If the console
is programmed to allow 8-second group calls on a particular channel, then whenever a paging sequence is
generated that consists of two tones of the same frequency, the page consists of an 8 second burst of that
tone frequency.
However, 8-second group calls do not apply when the GE code plan has been selected. In the GE system,
a “diagonal” tone of 742.5 Hz is inserted in place of the first tone if that tone is the same as the second
tone.
Example 2
Suppose the number of 2-Tone keypad digits accepted from the user on the selected channel is 2 and the
GE code plan has been selected. The preset 2-Tone digit is 4.
Therefore, if the operator entered 55 as the paging digits and pressed the TRANSMIT button, the console
would send the 2-Tone sequence A = 742.5 Hz, B = 907.5 Hz. This would alert a pager with a GE
capcode of 455.