Nortel DMS-100 Series Maintenance Manual page 65

negative coin check
The RCS transmits the following signals to the SMS in response to SMS
signals:
on-hook
off-hook
coin ground
unequipped
These signaling states are associated with specified A-bit and B-bit patterns.
The Bell Communications Research document Digital Interface Between the
SLC-96 Digital Loop Carrier System and a Local Digital Switch describes
these patterns. The RCS can receive a pattern on a DS-1 channel. If this
event occurs the line card of the channel places a voltage on the tip-ring pair.
These voltages can be negative or positive. These voltages can cause
operations like ringing, coin return, or coin collect to occur.
Both CDF and CMF lines use the SCD233 coin card. The card contains one
line circuit. An RCS shelf that operates in Modes I or III can contain a
maximum of 12 SCD233 coin cards. The four shelves of a fully equipped
RCS can contain a maximum of 48 coin cards. This information applies to
shelves that operate in Modes I or III
In Mode II, you must place coin cards in one of the four slots on the right
side of an RCS shelf. When you first plug in the coin card, the card receives
a permanent DS-1 channel.
Dial tone first Loop
A dial tone first (CDF) loop starts in a negative loop mode with –48 V on
the ring side. The CDF starts with a grounded tip side. When the subscriber
lifts the telephone handset, switchhook contacts and coin equipment relays
establish a current path from ring to tip.
The RCS detects a change in current that the CDF loop sends. This change
in current indicates an off-hook. The RCS sends a pattern of A-bits and
B-bits to the 8085 microprocessor. The 8085 microprocessor is in the
A/B-DDL message card. This A-bit and B-bit pattern notifies the
microprocessor if the subscriber goes off-hook.
The SMS A/B-bit facility detects this origination through the 8085
microprocessor. The SMS 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.
DMS-100 Family SMS Maintenance Manual XPM10 and up
Maintenance overview 1-49