Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


CTP151 Serial Interface Module


The Juniper Networks CTP151 Circuit to Packet platform optionally includes a replaceable CTP150–IM-SER serial interface module that can be paired with another module of the same type or a T1/E1 interface module. The serial interface module also has the option of supporting two multiservice daughter cards for 4-KHz or high-quality analog audio, or interrange instrumentation group (IRIG) signals. See CTP151 Multiservice Interface Module for details.

The four-port serial interface module supports individual cabling for each port. The CTP151 ports have small serial ports for HD-26 26-pin connectors (see Figure 1). The lowest-numbered port (marked 0) is at the bottom left, and the highest-numbered port (marked 3) is at the top right.

Figure 1: CTP151 Serial Interface Module
CTP151 Serial Interface Module
Four small serial ports and one clock reference port

The software-selectable interfaces for the module are RS-232/V.24, EIA530/X.21, EIA530A, and V.35. Software-selectable rates range from 50 bps to 12.228 Mbps.

The module also includes an external clock reference port (CLK) for an HD-26 connector.


The external clock reference port must be used only on the module in slot 0, the left-most slot on the front of the CTP151 chassis. For information about the CTP151 modules slot numbering, see CTP151 Modules Slot and Port Numbering.

On the CLK port, differential clock signals are output on the pins 4 and 17 of the HD-26 connector. When an EIA-530A DCE-F serial cable (CTP150-CBL-DB25-DCE-F) is connected to the CLK port, the TT pins 24 and 11 of the DB25 connector output clock signals. If you configure a 32 kHz reference output, an RS-422 32 kHz clock signal is generated on the pins. Even if you disable the 32 kHz reference output and configure an external clock reference, the module expects an RS-422 clock input (of the configured frequency) on the same pins.