74 Installation TB9100/P25 CG/P25 TAG Installation and Operation Manual
© Tait Limited March 2014
When the console system wishes to turn on the transmitter, it closes the
Press to Talk (PTT) Relay. The corresponding Tx Key Relay in the base
station or gateway closes and transmission commences. Transformer isolated
audio is modulated onto the transmitter carrier. When the PTT relay is
released, the transmission will cease. (Note: The base station or gateway uses
solid state relay equivalents). When the receiver detects a call, the Rx Call
relay closes, indicating to the console system that receive audio is available
on the console system’s transformer-coupled input.
The Tx Key input to the base station or gateway is current-limited internally
and does not require a current-limiting resistor in series. However, the Rx
Gate output has no current-limiting circuitry, so a series resistor may be
required to limit the current to less than ±120mA to prevent damage. The
value of this resistor is dependent on the battery voltage (normally between
10V and 50V), the internal resistance of the Rx call contact, and any
resistance of the Rx call relay.
This current limiting resistance may be integral to the external equip-
ment. Refer to the manufacturer’s documentation for details.
Tx Key relay
From RF Rx
To RF Tx
Rx gate contact
input for PTT (±10-50V)
±10-50V
line out (-20 to +10dBm)
Rx Gate output
(<35 resistance
when gate active)
Ω
line in (-20 to +10dBm)
internal current
limiting circuitry
current-limiting
resistor
(if required)
Rx call
relay
PTT relay
<35 internal
resistance
Ω
base station/gateway console system
1
2
3
4
5
6
7
8
base station/gateway
To Next Page
Loading...
Need help?
General
