Nortel DMS-100 Series Maintenance Manual page 66

1-50 Maintenance overview
The subscriber can begin to dial. The subscriber must deposit the correct
number of coins for a local call before dialing completes. If the subscriber
does not deposit the correct amount a recording activates. The recording
instructs the subscriber to start the call again and deposit the correct amount.
The cycle of this announcement occurs two times. If the subscriber does not
deposit the required amount at the end of two announcements, the system
disconnects the call.
The DMS-100 switch checks for coin presence through a negative coin
check on the SCD233 coin card. The 8085 microprocessor sends an A-bit
and B-bit pattern to the RCS. The A- and B-bit pattern requests that the
RCS check for coin presence. If the RCS finds a coin, specified contacts
close in the coin telephone set. The RCS detects a ground signal. The RCS
sends a signaling pattern of A-bits and B-bits to the 8085 microprocessor.
The signaling pattern associates with the coin ground signal. The signaling
pattern indicates that the subscriber deposited a coin. The A/B-bit facility
scans the coin ground pattern. The A/B-bit facility sends a message to the
TPT. The message indicates that the A/B-bit facility received a coin ground
pattern. The TPT informs the CM that the A/B-bit facility received a coin
ground pattern.
If the RCS does not detect a coin ground pattern, the subscriber receives a
recording.
Coin first line
A coin first (CMF) line begins in ground start mode with -48 V on the ring
side of the loop. The tip side is open.
When a subscriber lifts the telephone handset, the RCS does not detect
origination unless the subscriber deposits the correct number of coins.
When the subscriber deposits the correct number of coins, specified
switchhook contacts and coin set relays establish a current path. The current
path is from ring to ground. The RCS detects the ground current. The RCS
sends a signaling pattern to the 8085 microprocessor. This signaling pattern
indicates that ground current is present.
The A/B-bit facility detects the origination. The A/B-bit facility sends a
message to the TPT. The TPT informs the CM of the origination. The CM
directs the TPT to connect dial tone to the subscriber line.
297-8231-550 Standard 09.01 August 1998