IBM 1 Series - Teletypewriter Adapter Electrical Characteristics; Teletypewriter Adapter Communications Lines

Teletypewriter Adapter Electrical Characteristics
CAUTION: Refer to the engineering machine logic diagrams (MLDs) for
positive cable connector-pin designations.
Teletypewriter Adapter Communications Lines
The teletypewriter adapter offers two current-loop interfaces (or ‘‘ports’’)
and two voltage-level interfaces for connecting to user’s devices:
¢ Isolated current loop
« Nonisolated current loop
e EIA voltage level
e TTL voltage level
The teletypewriter adapter provides a 16-pin (2 x 8) top-card connector
for connecting the user’s device.
A separate pin or pair of pins on the top-card connector provides the
inputs and outputs for the four different interfaces.
Input Circuits General Description
4-22 GA34-0033
Figure 4-2 shows the four basic types of receive inputs: isolated contact
sense, nonisolated contact sense, TTL, and EIA RS232-C voltage level.
Input options are selected:
e By connecting to the appropriate pins, and
e By a 3-bit, coded jumper-pin selection on the card. See “Jumper
Selections” in this section for a detailed explanation of jumpering.
Isolated Contact Sense. Two connector pins are available for the signal
input. The isolated common may be strapped to signal ground on the
user’s connector, if desired in certain applications. When the isolated
contact sense input is used, some external non-IBM supplied power source
must be used to generate current for the receive current loop.
The equivalent circuit for the TTY-attachment card isolated contact sense
inputs is a series resistance between the input pins.
Nonisolated Contact Sense. Two connector pins are available for the signal
input. These inputs are used when it is desired that the teletypewriter
adapter card generate current for the receive current loop.
The equivalent circuit for the TTY-attachment card nonisolated contact
sense inputs is a resistor in series with a voltage source.