DCB PTT24 Посібник - Сторінка 3

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Chapter 1
Introduction
This chapter provides an overview of features and capabilities.
T
he PTT24 is a Push-to-Talk lockout device. It is used with multiple E&M circuits linked to
radio transmitters, PBXs, etc. The PTT-24 solves the problem of E&M leads being locked
into a Transmit ON state when a T1 circuit fails. Many T1 trunk lines will go into a busy
condition when the T1 trunk fails. This causes the E&M leads to lock in an ON state, which
causes radio transmitters to lock in the ON state, tie lines to go off hook, etc.
12 or 24 E&M ports are wired through the PTT Lockout unit. A front panel toggle
switch is used to select 12 or 24 port operation. A 2 digit push button switch is used to select
the E&M DS0 control channel. The Power LED flashes if an invalid control channel number
is selected.
Based on the selected E&M DS0 control channel (via the front panel) the PTT
Lockout device will detect a closure to ground on that channel and de-assert all the other
channels. E&M Type III is not supported.
In the PTT-24 12 channel mode, selecting control channel 1 through 12 will select one
of the even numbered leads 26 though 48 as the control channel. The other 11 even
numbered leads will be de-asserted if the control channel is asserted. All other leads are
passed straight through.
In the PTT-24 24 channel mode, selecting control channel 1 through 24 will select one
of the leads 26 though 49 as the control channel. The other 23 leads will be de-asserted if the
control channel is asserted. All other leads are passed straight through.
If the PTT-24 were to lose power, the E-leads will be in a pass through mode as
though the PTT-24 is only a "lump in the cable".
Lockout can be triggered by the E&M control channel being activated or the alarm
input. For both the control channel and the alarm input, there is a delay of 20 milliseconds
before the lockout occurs. The de-activation delay is 5 seconds. The de-activation delay
eliminates lockout "chattering" on/off/on/off, etc.
Leads 1 through 24 and 50 of the 50 pin Amphenol telco connectors are passed
straight through from the channel bank to the transmitter. The PTT24 does not impact these
leads in any way.
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