IBM 1 Series - Power Supplies

Baud-Rate Tolerance
The worst-case baud-rate (bit-time) tolerances for all attached devices
must be less than +2.0%.
Since bit-time tolerances are normally cumulative, this means that the
tenth bit (the stop bit) may occur anywhere from 20% early to 20% late.
Data Rise and Fall Times
Current loop—the rise time of a bit (defined as the time to switch from 1
mA to 12 mA) must be less than 3% of one bit time. The fall time (the
time to switch from 12 mA to 1 mA) must also be less than 3% of one bit
time.
TTL—the rise time of a bit (defined as the time to switch from 0.45 to
2.40 volts) must be less than 3% of one bit time. The fall time (time to
switch from 2.40 to 0.45 volt) must also be less than 3% of one bit time.
EIA—the data rise and fall times must conform to EIA RS232-C/CCITT
V.24 specifications.
Power Supplies
The teletypewriter adapter does not require any external power supplies.
All power required by the teletypewriter adapter is obtained from the I/O
card file in which the card is inserted.
The only exception to this is when the user elects to attach the device to
the isolated current loop interface. In this case, the user must supply a
25-volt (100-mA) power supply and a current-limiting resistor for both the
transmit and the receive loops.
The value of the series resistor must limit the current in each loop to 20
mA. Figure 4-8 shows the current loop connections.
‘Connections for current loop when the user supplies current
Teletypewriter adapter H/0 device
ASR |ASR
I3 35
A7T| 1 it +
SSSclosed = data mark — Receive — X7 T7
BS Transmit —
Signal ground “O Receive + X6 T8
Al} Receive + ,
Isolated receive input + —O Transmit — X3 T5
A3| Receive —
Isolated
receive
input
—
Transmit
+
X4
T6
e
ASR 33 cable connections
from ASR 33 wiring diagram
ASR 35 cable connections
from ASR 35 schematic
Figure 4-8. Connections for current loop when the user supplies current for the loop
4-28 GA34-0033