Equipment specification and operation
Page 19 of 64
Centralized Attendant Service Description and engineering
The RLT recognizes an increase in the DC resistance across the tip and ring
leads from 1300
Ω
or less to 20-K
Ω
or more as an on hook signal. The on
hook signal should be timed for 200 ms to 1.0 second. If the conductor loop
resistance changes back to low resistance (off hook) in this interval, the RLT
interprets that as a flash signal from the CAS attendant.
When the RLT has been seized for an incoming CO call, a dial “0” call, an
intercept call, or a hold recall after the CAS attendant has talked to the calling
party, the detection of the first flash signal prompts the connection of a
Digitone receiver to the RLT and splits the calling party away from the RLT.
A dial tone is sent to the CAS attendant when the Digitone receiver is
available to receive address signals. The dial tone is removed within 50 ms of
the start of dialing the first address character. If the RLT detects a subsequent
flash signal while connected to a receiver—that is, an attendant flash to clear
the receiver—it disconnects the receiver and returns to its initial state
(connection with the calling party).
When the receiver has translated the dialed address characters, different
confirmation tones are sent to the CAS attendant, depending on the status of
the called telephone.
Disconnect
The RLT recognizes and times an increase in the DC resistance across the tip
and ring leads from 1300
Ω
or less to 20-K ohms or more as an on hook from
the CAS attendant. If the on hook lasts longer than the flash timer, the RLT
interprets the change as a disconnect.
After interpreting disconnect from the attendant, the RLT opens the tip and
ring leads to the interfacing CO trunk at the Main site, sending a disconnect
signal to the Main site. To prevent the RLT from being seized from a new call
before the CO trunk at the Main site has released, the RLT provides a busy
guard timer.
Operation at the Main site
Idle state
There is a resistance greater than 20-K ohms across the tip and ring leads at
the CO trunk interface during the idle state.
EquipSp.BDY Page 19 Tuesday, January 14, 1997 9:16 AM
